The Treasury could pocket 20 million a year in extra fines once the country’s speed camera network is expanded. Motoring organizations warned that the (1) could become a poll tax on wheels, (2) huge number of drivers. There could be many more incidents of vandalism (3) cameras. The warnings came (4) a Daily Mail survey found almost all the 23 police forces in England and Wales were either (5) to expansion plans or considering (6) . Nationwide, the number of speeding tickets is expected to treble, (7) 90 million a year. (8) the scheme, police keep some of the cash from fines to 9 the costs of fitting and maintaining extra cameras and (10) that existing ones always have film in them. The rest will go to the Treasury. Both Ministers and police insist the scheme is aimed (11) at making roads safer. They point to trials in eight areas which cut collisions by a quarter and deaths and serious injuries by (12) a half. But motoring organizations fear cameras will be sited on relatively safe (13) fast stretches to catch as many drivers as possible. Some forces are also expected to 14 the "threshold" speeds at which cameras are (15) to the absolute legal minimum-15 mph in a 10 mph limit, and 26 mph in a 20 mph zone. This could encourage drivers to stare at their speedometers instead of concentrating on the road, and (16) to more accidents. Sue Nicholson, head of campaigns at the RAC, said, "We don’t have a problem with speed cameras (17) . But we do have concerns about (18) they are sited. Police risk losing credibility (19) motorists if cameras are seen as revenue-raising (20) safety devices./ （11）（）

已知商品的需求量D和供给量S都是价格p的函数D=Dp=s=sp=bp其中a＞0b＞0为常数价格p是时间t的函数且满足方程k为正常数．①假设当t=0时价格为1．试求需求量等于供给时量时的均衡价格pe

设随机变量X在区间[-13]上服从均匀分布则|X|的概率密度是______．

设ABC是三个两两相互独立的事件且PABC=00＜PC＜1则一定有______．

设X1X2Xn是总体N01的简单随机样本记T=则ET的值为______

设AB为n阶对称矩阵下列结论不正确的是______

设n=12则下列级数中肯定收敛的是______

AB均是n阶矩阵且A2-2AB=E则秩rAB-BA+A=______．

设X1X2Xn为来自总体N0σ2的样本则样本二阶原点矩的方差为______

已知线性方程组AX=kβ1+β2有解其中A=则k等于______

设fx在-∞0]上连续且满足求fx及其极小值

设fx在ab内可微且fa=fb=0f’a＜0f’b＜0则方程f’x=0在ab内______．

设函数fx在x=2的某邻域内可导且f’2=0又=-2则f2______．

设随机变量ξ的分布密度为求系数A

设A=ijn×n是正交矩阵将A以行分块为A=α1α2αnT则方程组AX=bb=b1bnT的通解为______

已知随机变量X和Y相互独立则X～N11Y～N14又PaX+bY≤0=则a与b应满足关系式______

Donotsignyourownnameattheendoftheletter.UseDepartmentofChineseLanguageandLiteratureinstead. Donotwritetheaddress.

已知yt=c1+c2at是差分方程yt+2-3y+1+2yt=0的通解则a=______．

Chronicinsomniaisamajorpublichealthproblem.Andtoomanypeopleareusing1therapiesevenwhilethereareafewtreatmentsthatdowork.MillionsofAmericans2awakeatnightcountingsheeporhaveastiffdrinkor3anpillhopingitwillmakethemsleepy.4expertsagreeallthatself-medicatingisabadideaandthecausesofchronicinsomniaremain5.a Chronicinsomniaisamajorpublichealthproblem.Andtoomanypeopleareusing1therapiesevenwhilethereareafewtreatmentsthatdowork.MillionsofAmericans2awakeatnightcountingsheeporhaveastiffdrinkor3anpillhopingitwillmakethemsleepy.4expertsagreeallthatself-medicatingisabadideaandthecausesofchronicinsomniaremain5. Almostathirdofadultshavetroublesleepingandabout10percenthave6ofdaytimeimpairmentthatsignaltrueinsomnia.But7thecomplaintsscientistsknowsurprisinglylittleaboutwhatcauseschronicinsomniaitshealthconsequencesandhowbesttotreatitapanelofspecialists8togetherbytheNationalInstitutesofHealthconcludedWednesday.Thepanelcalled9abroadrangeofresearchintoinsomnia10thatifscientistsunderstoodits11causestheycoulddevelopbettertreatments. Mostbutnotallinsomniaisthoughtto12otherhealthproblemsfromarthritisanddepressiontocardiovasculardisease.Thequestionofteniswhethertheinsomniacamefirstorwasaresultoftheotherdiseasesandhowtroublesleepingin13complicatesthoseotherproblems.Otherdiseases14theriskofinsomniaseemstoincreasewithageandtobemore15amongwomenespeciallyaftertheir50s.Smokingcaffeineandnumerous16drugsalsoaffectsleep. TheNIHisspendingabout$200millionthisyearonsleep-relatedresearchsome17tospecificdisordersandothers18theunderlyingscientificlawsthatcontrolthenervoussystemofsleep.Theagencywas19thepane’sreviewbeforedecidingwhatadditionalworkshouldbe20atinsomnia. 15

设随机变量X的分布函数为对X独立观测3次则3次结果都不超过1的概率为______．

设fuv具有连续偏导数且f’uuv+f’vuv=sinu+veu+v求yx=e-2xfxx所满足的一阶微分方程并求其通解

二次型fx1x2x3=x12+4x22+4x32-4x1x2+4x1x3-8x2x3的规范型是______

若|f’x|＜g’xx≥a则当x＞a时必有______

设A是n阶正定矩阵E是n阶单位阵证明A+E的行列式大于1

方程=0在区间01内的实根个数为______

设X1X2Xn是取自总体X的简单随机样本X的概率密度为-∞＜x＜+∞λ＞0．试求λ的矩估计

设=5则=______．

设微分方程yx是方程Y+x-1Y’+x2y=ex满足y0=0y’0=1的解则______

Donotsignyourownnameattheendoftheletter.UseLiMinginstead. Donotwritetheaddress

用配方法化二次型fxyz=x2+2y2+5z2+2xy+6yz+2zx为标准形并求所用的可逆线性变换．

已知矩阵B满足BA*+2A-1=B其中A*是A的伴随矩阵则|B|=______．

已知f’x=arctanx-12f0=0则fxdx=______．

设随机变量X服从02上的均匀分布Y服从参数λ=2的指数分布且XY相互独立记随机变量Z=X+2Y.求Z的概率密度

假设一部机器在一天内发生故障的概率为0.2机器发生故障时全天停止工作若一周5个工作日里无故障可获利润10万元发生一次故障仍可获利润5万元发生二次故障所获利润为0元发生三次或三次以上故障就要亏损2万元求一周内期望利润是多少

设α1=1231Tα2=112-1Tα3=13a3Tα4=357-1Tβ=011bTⅠ当ab满足什么条件时β可由α1α2α3α4线性表示且表示式唯一Ⅱ当ab满足什么条件时β可由α1α2α3α4线性表示且表示式不唯一并求出β的表示式

Themythologyofaculturecanprovidesomevitalinsightsintothebeliefsandvaluesofthatculture.Byusingfantasticandsometimesincrediblestoriestocreateanoraltraditionbywhichtoexplainthewondersofthenaturalworldandteachlessonstoyoungergenerationsasocietyexposesthoseideasandconceptsheldmostimportant.Justasimportantasthefinallessontobegatheredfromthestorieshoweverarethecharactersandtherolestheyplayinconveyingthatmessage.PerhapstheepitomeofmythologyanditsuseasatooltopassonculturalvaluescanbefoundinAesop’sFablestoldandretoldduringtheeraoftheGreekEmpire.Aesopaslavewhowonthefavorofthecourtthroughhisimaginativeanddescriptivetalesalmostexclusivelyusedanimalstofilltherolesinhisshortstories.Humanswhenatallpresentalmostalwaysplayedthepartofbumblingfoolsstrugglingtolearnthelessonbeingpresented.ThischoiceofcharacterizationallowsustoseethattheGreeksplacedwisdomonalevelslightlybeyondhumansimplyingthatdeepwisdomandunderstandingisauniversalqualitysoughtbyratherthansteanningfromhumanbeings.Aesop’sfablesillustratedthecentralthemesofhumilityandself-reliancereflectingtheimportanceofthosetraitsinearlyGreeksociety.Thefollyofhumanswasusedtocontrastagainsttheultimategoalofattainingahigherlevelofunderstandingandawarenessoftruthsaboutnatureandhumanity.Forexampleonenotablefablefeaturesafoxrepeatedlytryingtoreachabunchofgrapesonaveryhighvine.Afterfailingatseveralattemptsthefoxgivesupmakingupitsmindthatthegrapeswereprobablysouranyway.Thefable’slessonthatweoftenplaydownthatwhichwecan’tachievesoastomakeourselvesfeelbetterteachesthereaderorlistenerinanentertainingwayaboutoneoftheweaknessesofthehumanpsyche.ThemythologyofotherculturesandsocietiesrevealtheunderlyingtraitsoftheirrespectiveculturesjustasAesop’sfablesdid.ThestoriesofRomangodsAztecghostsandEuropeanelvesallservedtotrainancientgenerationsthoselessonsconsideredmostimportanttotheircommunityandtodaytheyofferapowerfullookingglassbywhichtoevaluateandconsiderthecontextualenvironmentinwhichthosecultureexisted.Theauthorappearstoviewfablesas

设A=则A2011-2A2010=______

设随机变量XY相互独立X在区间[05]上服从均匀分布Y服从参数为1的指数分布令Z=maxXY.计算PX+Y＞1

矩阵A=与下面矩阵______相似．

A=Am×nRA．=rb为m维列向量则有______

函数fxy=在点00处______．

=______．

计算D是下图中的阴影区域．

设X服从正态分布N022而X1X2X15为来自总体X的简单随机样本则随机变量所服从的分布为______

已知三元二次型fx1x2x3=XTAX矩阵A的对角元素之和为3且AB+B=0其中B=求出此二次型

设函数y=yx由方程组所确定试求．

设二次型的正负惯性指数都是1则a=______

设向量组Ⅰα1α2αs的秩为r1向量组Ⅱβ1β2βs的秩为r2且向量组Ⅱ可由向量组Ⅰ线性表示则______

OneofthemostpressingchallengesthattheUnitedStates—andindeedtheworld—willfaceinthenextfewdecadesishowtoalleviatethegrowingstressthathumanactivitiesareplacingontheenvironment.Theconsequencesarejusttoogreattoignore.Wildlifehabitatsarebeingdegradedordisappearingaltogetherasnewdevelopmentstakeupmoreland.PlantandanimalspeciesarebecomingextinctatagreaterratenowthanatanytimeinEarth’shistory.Asmanyas30percentoftheworld’sfishstocksareoverexploited.Andthelistgoeson.Yetthereisreasontohavehopeforthefuture.Advancesincomputingpowerandmolecularbiologyareamongthetremendousincreasesinscientificcapabilitythatarehelpingresearchersgainabetterunderstandingoftheseproblems.Recentdevelopmentsinscienceandtechnologycouldprovidethebasisforsomemajorandtimelyactionsthatwouldimproveourunderstandingofhowhumanactivitiesaffecttheenvironment.Onepriorityforresearchisimprovinghydrologicalforecasting.Ithasbeenestimatedthattheworld’swaterusecouldtripleinthenexttwodecades.AlreadywidespreadwatershortageshaveoccurredinpartsofChinaIndiaNorthAfricaandtheArabianPeninsula.TheneedforwateralsoistakingitstollonfreshwaterecosystemsintheUnitedStates.Only2percentofthenation’sstreamsareconsideredingoodconditionandcloseto40percentofnativefishspeciesareraretoextinct.Usingavarietyofnewremotesensingtoolsscientistscanlearnmoreabouthowprecipitationaffectswaterlevelshowsurfacewaterisgeneratedandtransportedandhowchangesinthelandscapeaffectwatersupplies.Topreventoutbreaksofinfectiousdiseasesinplantsanimalsandhumansmorestudyisneededonhowpathogensparasitesanddisease-carryingspecies—aswellashumansandotherspeciestheyinfect—areaffectedbychangesintheenvironment.Theoveruseofantibioticsbothinhumansandinfarmanimalshascontributedtothegrowthofantibiotic-resistantmicroorganisms.Researcherscantakeadvantageofnewtechnologiesingeneticsandcomputingtobettermonitorandpredicttheeffectsthatenvironmentalchangesmighthaveondiseaseoutbreaks.HumanshavemadealterationstoEarth’ssurface—suchastropicaldeforestationreductionofsurfaceandgroundwaterandmassivedevelopment—sodramaticthattheyapproachthelevelsoftransformationthatoccurredduringglacialperiods.Suchalterationscausechangesinlocalandregionalclimateandwilldeterminethefutureofagriculture.Recentadvancesindatacollectionandanalysisshouldbeusedtodocumentandbetterunderstandthecausesandconsequencesofchangesinlandcoveranduse.ThepoorconditionofstreamsintheU.S.canbeattributedto

Upuntilafewdecadesagoourvisionsofthefuturewerelargely—thoughbynomeansuniformly—glowinglypositive.Scienceandtechnologywouldcurealltheillsofhumanityleadingtolivesoffulfillmentandopportunityforall.Nowutopiahasgrownunfashionableaswehavegainedadeeperappreciationoftherangeofthreatsfacingusfromasteroidstriketoepidemicflutoclimatechange.Youmightevenbetemptedtoassumethathumanityhaslittlefuturetolookforwardto.Butsuchgloominessismisplaced.Thefossilrecordshowsthatmanyspecieshaveenduredformillionsofyears—sowhyshouldn’tweTakeabroaderlookatourspecies’placeintheuniverseanditbecomesclearthatwehaveanexcellentchanceofsurvivingfortensifnothundredsofthousandsofyears.LookupHomosapiensintheRedListofthreatenedspeciesoftheInternationalUnionfortheConversationofNatureIUCNandyouwillread:ListedasLeastConcernasthespeciesisverywidelydistributedadaptablecurrentlyincreasingandtherearenomajorthreatsresultinginanoverallpopulationdecline.SowhatdoesourdeepfutureholdAgrowingnumberofresearchersandorganizationsarenowthinkingseriouslyaboutthatquestion.ForexampletheLongNowFoundationhasitsflagshipprojectamechanicalclockthatisdesignedtostillbemarkingtimethousandsofyearshence.Perhapswillfullyitmaybeeasiertothinkaboutsuchlengthytimescalesthanaboutthemoreimmediatefuture.Thepotentialevolutionoftoday’stechnologyanditssocialconsequencesisdazzlinglycomplicatedandit’sperhapsbestlefttosciencefictionwritersandfuturologiststoexplorethemanypossibilitieswecanenvisage.That’sonereasonwhywehavelaunchedArcanewpublicationdedicatedtothenearfuture.Buttakealongerviewandthereisasurprisingamountthatwecansaywithconsiderableassurance.Assooftenthepastholdsthekeytothefuture:wehavenowidentifiedenoughofthelong-termpatternsshapingthehistoryoftheplanetandourspeciestomakeevidence-basedforecastsaboutthesituationsinwhichourdescendantswillfindthemselves.Thislongperspectivemakesthepessimisticviewofourprospectsseemmorelikelytobeapassingfad.Tobesurethefutureisnotallrosy.Butwearenowknowledgeableenoughtoreducemanyoftherisksthatthreatenedtheexistenceofearlierhumansandtoimprovethelotofthosetocome.Ourvisionofthefutureusedtobeinspiredby

设fx在-∞+∞内是可导的奇函数则下列函数中是奇函数的是______

Collegegraduatesarenowleavingschoolwithnotonlyadiplomabutalsowithmoredebtthaninanyotherperiodinhistory.AccordingtotheCollegeBoardaveragefinancialaidperfulltimeequivalentstudentadjustedforinflationhasalmostdoubledinthelastdecade.Additionallynotonlyistheaveragestudentdebtloadhigherbutalsothenumberofloansoriginatedincreasedbynearlyfourfold.Thusstudentlendinghasincreasedinbreadthaswellasdepthdoublyimpactingthefinancialsituationsofthosestudentswhomustdependonstudentloanstofinancetheireducation.Furthermorethesefiguresnodoubtunderstatethetruelevelofindebtednessincurredbystudentsandtheirfamiliessincesomeundoubtedlyfinancepartoftheireducationandlivingexpensesthroughtheuseofconsumerloanshomeequityloansorcreditcards.Thusthealreadyhugeburdenofstudentloandebtincurredbystudentsandtheirfamiliesisexacerbatedbyfinancialobligationsfromothersources.Thissituationistheoutcomeofaprecariouscombinationofeasycreditthankstocardissuerswhoareeagertotapintothislucrativemarketfinancialnaivetéonthepartofstudentsandasenseonbothsidesthatifworsecomestoworsemommyanddaddywillstepinandsetthingsright.Allcombinetomakecreditatemptingluretostudentsstrappedforcash.Whilecreditstillremainavirtualelementforthefinancingofmanystudents’educationatexpensivecollegesitsimplicationsmustcarefullyweighedandconsideredlestthecash-poorstudentfindhimselfwithmorethathebargainedfor.MoststudentsintheUnitedStatesattendcollegeswhosetuitiondoesnotexceed$15000however.Neverthelessrisingpricescombinedwithstagnantincomegainsamonglow-andmoderate-incomefamilieshavemadeitdifficultifnotimpossibleforastudentfromafamilyofsuchanincomelevelastudentwhohasthemosttogainfromacollegeeducationtoattendcollegewithoutsignificantlyaddingtothefinancialburdenofhisorherfamily.Whilestudentloansstillremainavitalelementforthefinancingofmanystudents’educationatexpensivecollegesitsimplicationsmustbecarefullyweighedandconsideredlestthecash-poorstudentfindhimselfwithmorethanhebargainedfor.Theauthorviewsstudentloansas

=______

设n阶实对称矩阵A的秩为r且满足A2=A求Ⅰ二次型xTAx的标准形Ⅱ行列式|E+A+A2++An|的值其中E为单位矩阵

设ab为正常系数λ为非负常数微分方程Ⅰ求该方程的通解Ⅱ证明当λ=0时当λ＞0时

设且F可微证明

电话公司有300台分机每台分机有6%的时间处于与外线通话状态设每台分机是否处于通话状态相互独立用中心极限定理估计至少安装多少条外线才能保证每台分机使用外线不必等候的概率不低于0.95

积分的值等于______

______.

设随机变量ξ的分布密度为求Eξ和Dξ

设A为三阶矩阵α1α2α3为三维线性无关列向量组且有Aα1=α2+α3Aα2=α3+α1Aα3=α1+α2．求A的全部特征值

设fx在-∞+∞存在二阶导数且fx=-f-x当x＜0时有f’x＜0fx＞0则当x＞0时有______

Relativitytheoryhashadaprofoundinfluenceonourpictureofmatterbyforcingustomodifyourconceptofaparticleinanessentialway.46Inclassicalphysicsthemassofanobjecthadalwaysbeenassociatedwithanindestructiblematerialsubstancewithsomestuffofwhichallthingswerethoughttobemade.Relativitytheoryshowedthatmasshasnothingtodowithanysubstancebutisaformenergy.Energyhoweverisadynamicquantityassociatedwithactivityorwithprocesses.47Thefactthatthemassofaparticleisequivalenttoacertainofenergymeansthattheparticlecannolongerbeseenasastatic_objectbuthastobeconceivedasadynamicpatternaprocessinvolvingtheenergywhichmanifestitselfastheparticle’smass.48ThisnewviewofparticleswasinitiatedbyDiracwhenheformulatedarelativisticequationdescribingthebehaviorofelectrons.Dirac’stheorywasnotonlyextremelysuccessfulinaccountingforthefinedetailsofatomicstructurebutalsorevealedafundamentalsymmetrybetweenmatterandanti-matter.Itpredictedtheexistenceofananti-matterwiththesamemassastheelectronbutwithanoppositecharge.ThispositivelychargedparticlenowcalledthepositronwasindeeddiscoveredtwoyearsafterDirachadpredictedit.Thesymmetrybetweenmatterandanti-matterimpliesthatforeveryparticlethereexistsanantiparticleswithequalmassandoppositecharge.Pairsofparticlesandantiparticlescanbecreatedifenoughenergyisavailableandcanbemadetoturnintopureenergyinthereverseprocessofdestruction.49TheseprocessesofparticlecreationanddestructionhadbeenpredictedfromDirac’stheorybeforetheywereactuallydiscoveredinnatureandsincethentheyhavebeenobservedmillionsoftimes.Thecreationofmaterialparticlesfrompureenergyiscertainlythemostspectaculareffectofrelativitytheoryanditcanonlybeunderstoodintermsoftheviewofparticlesoutlinedabove.50Beforerelativisticparticlephysicstheconstituentsofmatterhadalwaysbeenconsideredasbeingeitherelementaryunitswhichwereindestructibleandunchangeableorascompositeobjectswhichcouldbebrokenupintotheirconstituentparts.Andthebasicquestionwaswhetheronecoulddividematteragainandagainorwhetheronewouldfinallyarriveatsomesmallestindivisibleunits.

=______

dxdx=______

若则f[φx]=______．

设A为三阶矩阵有三个不同特征值λ1λ2λ3对应的特征向量依次为α1α2α3令β=α1+α2+α3．βAβA2β线性无关

Chronicinsomniaisamajorpublichealthproblem.Andtoomanypeopleareusing1therapiesevenwhilethereareafewtreatmentsthatdowork.MillionsofAmericans2awakeatnightcountingsheeporhaveastiffdrinkor3anpillhopingitwillmakethemsleepy.4expertsagreeallthatself-medicatingisabadideaandthecausesofchronicinsomniaremain5. Almostathirdofadultshavetroublesleepingandabout10percenthave6ofdaytimeimpairmentthatsignaltrueinsomnia.But7thecomplaintsscientistsknowsurprisinglylittleaboutwhatcauseschronicinsomniaitshealthconsequencesandhowbesttotreatitapanelofspecialists8togetherbytheNationalInstitutesofHealthconcludedWednesday.Thepanelcalled9abroadrangeofresearchintoinsomnia10thatifscientistsunderstoodits11causestheycoulddevelopbettertreatments. Mostbutnotallinsomniaisthoughtto12otherhealthproblemsfromarthritisanddepressiontocardiovasculardisease.Thequestionofteniswhethertheinsomniacamefirstorwasaresultoftheotherdiseasesandhowtroublesleepingin13complicatesthoseotherproblems.Otherdiseases14theriskofinsomniaseemstoincreasewithageandtobemore15amongwomenespeciallyaftertheir50s.Smokingcaffeineandnumerous16drugsalsoaffectsleep. TheNIHisspendingabout$200millionthisyearonsleep-relatedresearchsome17tospecificdisordersandothers18theunderlyingscientificlawsthatcontrolthenervoussystemofsleep.Theagencywas19thepane’sreviewbeforedecidingwhatadditionalworkshouldbe20atinsomnia. 1

当x→0时fx=x-sinax与gx=x2ln1-bx是等价无穷小则______

设随机变量Xi～i=12且PX1X2=0=1则PX1=X2等于______．

已知在-∞+∞上存在原函数求常数A并求fx的原函数

Todaysome30%ofsmallbusinessownersdon’thaveaWebpresenceatallwhilethevastmajoritywhodoarewatchingtheirsitessitstalewaitingandwantingforbusiness.WheredidthingsgowrongTherearecommonprinciplesfollowedbythosewhosedreamsofonlinesuccesshavebecomereality.41Buildyoursitearoundyourcustomer:Thinkingofyoursiteasyouronlinestorefrontbuiltarounddeliveringthehighest-qualitycustomerexperiencefromthemomentyourcustomerstepsthroughthedoor.42Justbecauseyoubuiltitdoesn’tmeanthey’llcome:Ifyouaren’tseeingalargevolumeoftargetedtraffictoyoursiteit’stimetouptheante.43Integratecustomerloyaltyprogramsandpromotions:Methodscontaindiscountsnewsorfriendlyservicereminders.Usediscountpromotionalofferstostayintouchwithpastvisitorstoyoursite.44Justifyyourmonthlyspendingthroughproductbundling:Whilepay-per-clickInternetadvertisingismuchmorecost-effectivethantraditionalmediachannelsbundlingproductstogetherwillnotonlyincreaseyoursalesrevenuebutalsoenableyoutogetmoreoutofyourper-clickadrates.45Measureyourprogress:YoursitemaybelivebuthowisitperformingArmedwiththesesimplelessonsvowtomakeyourbusinessrealizethetruepromiseoftheInternet.A.Amanufacturingcompanyselling$50itemswashavingtroublejustifyingthecostofonlinekeywordads.Bybundlingproductstocreatepackagesof$100ormoreandadvertisingtowholesalecustomerslookingtobuyinbulkthemanufacturerdroppeditssalesrepresentativeagenciesandfocusedonlargevolumebuyerssuchasWal-MartandTarget.Needlesstosaythecompanyhadnotroubleexceedingitsyearlysalesquota.B.Oneofmypastclientshadawell-designedphysicalstorefrontsolidpricesandqualityofferings.Howeverhewasn’tabletodriveenoughstoretrafficdespitetargetedadvertisingeffortsinprintpublicationsandotherofflinevenues.Wedecidedtoshiftthoseaddollarstoanonlinepay-per-clickcampaign—inwhichtheadvertiserpayswheneversomeoneclicksonitsentrypostedduringthecourseofasitesearchbasedonkeywordsrelevanttohisbusiness.Theimmediateimpactwasstaggering.Onlinerevenuesoaredtenfoldto$1millionfrom$100000withinonlyafewmonths.C.Withtoday’stechnologyyourreturncanbeeasilymeasured.IfyourelyonyourWebsiteasasalestoolyoucan’taffordnottoinvestinsiteanalytics.MakesureyourWebsolutionincludesaneasy-to-usereportingtoolthatpresentsthisinformationinaclearconciseformat.AfterallwhilemetricsareacriticalpartoftheWebequationyoudon’thavethetimetospendhoursdiggingthroughreamsofdata.D.YearsagoIworkedwithawomanwhosoldpursesonlinethroughahome-builtsitethatlackedcriticale-commercecomponents.Afterasimpleredesignincludingproductdescriptionscomprehensivenavigationandasecureuser-friendlyorderingsystemherrevenueincreasedfivefold.Andshebeganreceivingravereviewsfromcustomersimpressedwiththeeaseandconvenienceoftheonlineshoppingexperience.E.Onlinesuccessdemandsmorethansimplepresence.YourInternetinvestmentshouldpayforitselfwithnewcustomersandincreasedsales.Findatrustedpartnerwhocanhelpyounavigatetoday’sandtomorrow’stechnologyandwhounderstandsthebottom-linerealitiesofyourbusiness.F.OnevillarentalcompanyhadaWebsitethatgeneratedveryfewcallsandonlinebookings.Ihelpedthecompanysetupalastminutedealsdistributionlist.Bysubscribingsitevisitorswouldreceiveweeklye-mailsoffering11th-hourdiscountsonvillarentals.Asaresultthecompanycapturedcontactinformationforthousandsofpossiblecustomersreduceditsunusedinventorytoalmostzeroandincreasedrevenuesignificantly.

Todaysome30%ofsmallbusinessownersdon’thaveaWebpresenceatallwhilethevastmajoritywhodoarewatchingtheirsitessitstalewaitingandwantingforbusiness.WheredidthingsgowrongTherearecommonprinciplesfollowedbythosewhosedreamsofonlinesuccesshavebecomereality.41Buildyoursitearoundyourcustomer:Thinkingofyoursiteasyouronlinestorefrontbuiltarounddeliveringthehighest-qualitycustomerexperiencefromthemomentyourcustomerstepsthroughthedoor.42Justbecauseyoubuiltitdoesn’tmeanthey’llcome:Ifyouaren’tseeingalargevolumeoftargetedtraffictoyoursiteit’stimetouptheante.43Integratecustomerloyaltyprogramsandpromotions:Methodscontaindiscountsnewsorfriendlyservicereminders.Usediscountpromotionalofferstostayintouchwithpastvisitorstoyoursite.44Justifyyourmonthlyspendingthroughproductbundling:Whilepay-per-clickInternetadvertisingismuchmorecost-effectivethantraditionalmediachannelsbundlingproductstogetherwillnotonlyincreaseyoursalesrevenuebutalsoenableyoutogetmoreoutofyourper-clickadrates.45Measureyourprogress:YoursitemaybelivebuthowisitperformingArmedwiththesesimplelessonsvowtomakeyourbusinessrealizethetruepromiseoftheInternet.A.Amanufacturingcompanyselling$50itemswashavingtroublejustifyingthecostofonlinekeywordads.Bybundlingproductstocreatepackagesof$100ormoreandadvertisingtowholesalecustomerslookingtobuyinbulkthemanufacturerdroppeditssalesrepresentativeagenciesandfocusedonlargevolumebuyerssuchasWal-MartandTarget.Needlesstosaythecompanyhadnotroubleexceedingitsyearlysalesquota.B.Oneofmypastclientshadawell-designedphysicalstorefrontsolidpricesandqualityofferings.Howeverhewasn’tabletodriveenoughstoretrafficdespitetargetedadvertisingeffortsinprintpublicationsandotherofflinevenues.Wedecidedtoshiftthoseaddollarstoanonlinepay-per-clickcampaign—inwhichtheadvertiserpayswheneversomeoneclicksonitsentrypostedduringthecourseofasitesearchbasedonkeywordsrelevanttohisbusiness.Theimmediateimpactwasstaggering.Onlinerevenuesoaredtenfoldto$1millionfrom$100000withinonlyafewmonths.C.Withtoday’stechnologyyourreturncanbeeasilymeasured.IfyourelyonyourWebsiteasasalestoolyoucan’taffordnottoinvestinsiteanalytics.MakesureyourWebsolutionincludesaneasy-to-usereportingtoolthatpresentsthisinformationinaclearconciseformat.AfterallwhilemetricsareacriticalpartoftheWebequationyoudon’thavethetimetospendhoursdiggingthroughreamsofdata.D.YearsagoIworkedwithawomanwhosoldpursesonlinethroughahome-builtsitethatlackedcriticale-commercecomponents.Afterasimpleredesignincludingproductdescriptionscomprehensivenavigationandasecureuser-friendlyorderingsystemherrevenueincreasedfivefold.Andshebeganreceivingravereviewsfromcustomersimpressedwiththeeaseandconvenienceoftheonlineshoppingexperience.E.Onlinesuccessdemandsmorethansimplepresence.YourInternetinvestmentshouldpayforitselfwithnewcustomersandincreasedsales.Findatrustedpartnerwhocanhelpyounavigatetoday’sandtomorrow’stechnologyandwhounderstandsthebottom-linerealitiesofyourbusiness.F.OnevillarentalcompanyhadaWebsitethatgeneratedveryfewcallsandonlinebookings.Ihelpedthecompanysetupalastminutedealsdistributionlist.Bysubscribingsitevisitorswouldreceiveweeklye-mailsoffering11th-hourdiscountsonvillarentals.Asaresultthecompanycapturedcontactinformationforthousandsofpossiblecustomersreduceditsunusedinventorytoalmostzeroandincreasedrevenuesignificantly.

如果

设方程x2=y2y确定y是x的函数则dy=______．

Themythologyofaculturecanprovidesomevitalinsightsintothebeliefsandvaluesofthatculture.Byusingfantasticandsometimesincrediblestoriestocreateanoraltraditionbywhichtoexplainthewondersofthenaturalworldandteachlessonstoyoungergenerationsasocietyexposesthoseideasandconceptsheldmostimportant.Justasimportantasthefinallessontobegatheredfromthestorieshoweverarethecharactersandtherolestheyplayinconveyingthatmessage.PerhapstheepitomeofmythologyanditsuseasatooltopassonculturalvaluescanbefoundinAesop’sFablestoldandretoldduringtheeraoftheGreekEmpire.Aesopaslavewhowonthefavorofthecourtthroughhisimaginativeanddescriptivetalesalmostexclusivelyusedanimalstofilltherolesinhisshortstories.Humanswhenatallpresentalmostalwaysplayedthepartofbumblingfoolsstrugglingtolearnthelessonbeingpresented.ThischoiceofcharacterizationallowsustoseethattheGreeksplacedwisdomonalevelslightlybeyondhumansimplyingthatdeepwisdomandunderstandingisauniversalqualitysoughtbyratherthansteanningfromhumanbeings.Aesop’sfablesillustratedthecentralthemesofhumilityandself-reliancereflectingtheimportanceofthosetraitsinearlyGreeksociety.Thefollyofhumanswasusedtocontrastagainsttheultimategoalofattainingahigherlevelofunderstandingandawarenessoftruthsaboutnatureandhumanity.Forexampleonenotablefablefeaturesafoxrepeatedlytryingtoreachabunchofgrapesonaveryhighvine.Afterfailingatseveralattemptsthefoxgivesupmakingupitsmindthatthegrapeswereprobablysouranyway.Thefable’slessonthatweoftenplaydownthatwhichwecan’tachievesoastomakeourselvesfeelbetterteachesthereaderorlistenerinanentertainingwayaboutoneoftheweaknessesofthehumanpsyche.ThemythologyofotherculturesandsocietiesrevealtheunderlyingtraitsoftheirrespectiveculturesjustasAesop’sfablesdid.ThestoriesofRomangodsAztecghostsandEuropeanelvesallservedtotrainancientgenerationsthoselessonsconsideredmostimportanttotheircommunityandtodaytheyofferapowerfullookingglassbywhichtoevaluateandconsiderthecontextualenvironmentinwhichthosecultureexisted.Themainpointofthistextis

某工厂生产甲乙两种产品当这两种产品的产量分别为x和y单位吨时的总效益函数为Rxy=15x+34y-x2-2xy-4y2-36单位万元．已知生产甲种产品每吨需支付排污费用1万元生产乙种产品每吨需支付排污费2万元．在不限制排污费用支出的情况下这两种产品的产量各为多少时总利润最大最大总利润是多少

若函数fx与gx在-∞+∞内可导且fx＜gx则必有______

已知某产品总产量的变化率为问在达到平均年产量最大时再生产3年求这3年的平均年产量．

设常数λ＞0且级数收敛则级数______

设A为三阶实对称矩阵且存在可逆矩阵使得又A的伴随矩阵A*有特征值λ0λ0所对应的特征向量为α=[25-1]T．计算A*-1

计算二重积分其中积分区域D由y轴与曲线y=y=围成

Collegegraduatesarenowleavingschoolwithnotonlyadiplomabutalsowithmoredebtthaninanyotherperiodinhistory.AccordingtotheCollegeBoardaveragefinancialaidperfulltimeequivalentstudentadjustedforinflationhasalmostdoubledinthelastdecade.Additionallynotonlyistheaveragestudentdebtloadhigherbutalsothenumberofloansoriginatedincreasedbynearlyfourfold.Thusstudentlendinghasincreasedinbreadthaswellasdepthdoublyimpactingthefinancialsituationsofthosestudentswhomustdependonstudentloanstofinancetheireducation.Furthermorethesefiguresnodoubtunderstatethetruelevelofindebtednessincurredbystudentsandtheirfamiliessincesomeundoubtedlyfinancepartoftheireducationandlivingexpensesthroughtheuseofconsumerloanshomeequityloansorcreditcards.Thusthealreadyhugeburdenofstudentloandebtincurredbystudentsandtheirfamiliesisexacerbatedbyfinancialobligationsfromothersources.Thissituationistheoutcomeofaprecariouscombinationofeasycreditthankstocardissuerswhoareeagertotapintothislucrativemarketfinancialnaivetéonthepartofstudentsandasenseonbothsidesthatifworsecomestoworsemommyanddaddywillstepinandsetthingsright.Allcombinetomakecreditatemptingluretostudentsstrappedforcash.Whilecreditstillremainavirtualelementforthefinancingofmanystudents’educationatexpensivecollegesitsimplicationsmustcarefullyweighedandconsideredlestthecash-poorstudentfindhimselfwithmorethathebargainedfor.MoststudentsintheUnitedStatesattendcollegeswhosetuitiondoesnotexceed$15000however.Neverthelessrisingpricescombinedwithstagnantincomegainsamonglow-andmoderate-incomefamilieshavemadeitdifficultifnotimpossibleforastudentfromafamilyofsuchanincomelevelastudentwhohasthemosttogainfromacollegeeducationtoattendcollegewithoutsignificantlyaddingtothefinancialburdenofhisorherfamily.Whilestudentloansstillremainavitalelementforthefinancingofmanystudents’educationatexpensivecollegesitsimplicationsmustbecarefullyweighedandconsideredlestthecash-poorstudentfindhimselfwithmorethanhebargainedfor.ThemainpointofParagraph4is

假设生产和销售某产品的收益R是产量的q二次函数经统计得知当产量q分别为024时总收入R分别为068万元试确定R与q之间的函数关系

求解差分方程yx+1+3yx=x·2x．

计算二重积分x2+ydσ其中D是由x2+y2=2y的上半圆直线x=-1x=1及x轴围成的区域．

幂级数的和函数为______

Sustainabledevelopmentisappliedtojustabouteverythingfromenergytocleanwaterandeconomicgrowthandasaresultithasbecomedifficulttoquestioneitherthebasicassumptionsbehinditorthewaytheconceptisputtouse.Thisisespeciallytrueinagriculturewheresustainabledevelopmentisoftentakenasthesolemeasureofprogresswithoutaproperappreciationofhistoricalandculturalperspectives.Tostartwithitisimportanttorememberthatthenatureofagriculturehaschangedmarkedlythroughouthistoryandwillcontinuetodoso.MedievalagricultureinnorthernEuropefedclothedandshelteredapredominantlyruralsocietywithamuchlowerpopulationdensitythanitistoday.Ithadminimaleffectonbiodiversityandanypollutionitcausedwastypicallylocalized.Intermsofenergyuseandthenutrientscapturedintheproductitwasrelativelyinefficient.Contrastthiswithfarmingsincethestartoftheindustrialrevolution.Competitionfromoverseasledfarmerstospecializeandincreaseyields.Throughoutthisperiodfoodbecamecheapersafeandmorereliable.Howeverthesechangeshavealsoledtohabitatlossandtodiminishingbiodiversity.What’smoredemandforanimalproductsindevelopingcountriesisgrowingsofastthatmeetingitwillrequireanextra300milliontonsofgrainayearby2050.Yetthegrowthofcitiesandindustryisreducingtheamountofwateravailableforagricultureinmanyregions.Allthismeansthatagricultureinthe21stcenturywillhavetobeverydifferentfromhowitwasinthe20th.Thiswillrequireradicalthinking.Forexampleweneedtomoveawayfromtheideathattraditionalpracticesareinevitablymoresustainablethannewones.Wealsoneedtoabandonthenotionthatagriculturecanbezeroimpact.Thekeywillbetoabandontherathersimpleandstaticmeasuresofsustainabilitywhichcentreontheneedtomaintainproductionwithoutincreasingdamage.Insteadweneedamoredynamicinterpretationonethatlooksattheprosandconsofallthevariouswaylandisused.Therearemanydifferentwaystomeasureagriculturalperformancebesidesfoodyield:energyuseenvironmentalcostswaterpuritycarbonfootprintandbiodiversity.ItisclearforexamplethatthecarbonoftransportingtomatoesfromSpaintotheUKislessthanthatofproducingthemintheUKwithadditionalheatingandlighting.Butwedonotknowwhetherlowercarbonfootprintswillalwaysbebetterforbiodiversity.Whatiscrucialisrecognizingthatsustainableagricultureisnotjustaboutsustainablefoodproduction.Specializationandtheefforttoincreaseyieldshaveresultedin

设λ1λ2是n阶矩阵A的特征值α1α2分别是A的属于λ1λ2的特征向量则______

Inapurelybiologicalsensefearbeginswiththebody’ssystemforreactingtothingsthatcanharmus—theso-calledfight-or-flightresponse.Ananimalthatcan’tdetectdangercan’tstayalivesaysJosephLeDoux.Likeanimalshumansevolvedwithanelaboratemechanismforprocessinginformationaboutpotentialthreats.Atitscoreisaclusterofneuronsdeepinthebrainknownastheamygdala. LeDouxstudiesthewayanimalsandhumansrespondtothreatstounderstandhowweformmemoriesofsignificanteventsinourlives.Theamygdalareceivesinputfrommanypartsofthebrainincludingregionsresponsibleforretrievingmemories.Usingthisinformationtheamygdalaappraisesasituation—Ithinkthischargingdogwantstobiteme—andtriggersaresponsebyradiatingnervesignalsthroughoutthebody.Thesesignalsproducethefamiliarsignsofdistress:tremblingperspirationandfast-movingfeetjusttonamethree. Thisfearmechanismiscriticaltothesurvivalofallanimalsbutnoonecansayforsurewhetherbeastsotherthanhumansknowthey’reafraid.ThatisasLeDouxsaysifyouputthatsystemintoabrainthathasconsciousnessthenyougetthefeelingoffear. HumanssaysEdwardM.Hallowellhavetheabilitytocallupimagesofbadthingsthathappenedinthepastandtoanticipatefutureevents.Combinethesehigherthoughtprocesseswithourhardwireddangerdetectionsystemsandyougetanear-universalhumanphenomenon:worry. That’snotnecessarilyabadthingsaysHallowell.Whenusedproperlyworryisanincredibledevicehesays.Afterallalittlehealthyworryingisokayifitleadstoconstructiveaction—likehavingadoctorlookatthatweirdspotonyourback. Hallowellinsiststhoughthatthere’sarightwaytoworry.Neverdoitalonegetthefactsandthenmakeaplan.Hesays.Mostofushavesurvivedarecessionsowe’refamiliarwiththebelt-tighteningstrategiesneededtosurviveaslump. Unfortunatelyfewofushavemuchexperiencedealingwiththethreatofterrorismsoit’sbeendifficulttogetfactabouthowweshouldrespond.That’swhyHallowellbelievesitwasokayforpeopletoindulgesomeextremeworrieslastfallbyaskingdoctorsforCiproandbuyinggasmasks. WhichofthefollowingisthebestwaytodealWithyourworriesaccordingtoHallowell

设fx+yxy=x2+y2+xy则dfxy=______．

设幂级数的收敛半径为2则级数a+1n的收敛区间为______

设函数fx连续则=______

Chronicinsomniaisamajorpublichealthproblem.Andtoomanypeopleareusing1therapiesevenwhilethereareafewtreatmentsthatdowork.MillionsofAmericans2awakeatnightcountingsheeporhaveastiffdrinkor3anpillhopingitwillmakethemsleepy.4expertsagreeallthatself-medicatingisabadideaandthecausesofchronicinsomniaremain5.a Chronicinsomniaisamajorpublichealthproblem.Andtoomanypeopleareusing1therapiesevenwhilethereareafewtreatmentsthatdowork.MillionsofAmericans2awakeatnightcountingsheeporhaveastiffdrinkor3anpillhopingitwillmakethemsleepy.4expertsagreeallthatself-medicatingisabadideaandthecausesofchronicinsomniaremain5. Almostathirdofadultshavetroublesleepingandabout10percenthave6ofdaytimeimpairmentthatsignaltrueinsomnia.But7thecomplaintsscientistsknowsurprisinglylittleaboutwhatcauseschronicinsomniaitshealthconsequencesandhowbesttotreatitapanelofspecialists8togetherbytheNationalInstitutesofHealthconcludedWednesday.Thepanelcalled9abroadrangeofresearchintoinsomnia10thatifscientistsunderstoodits11causestheycoulddevelopbettertreatments. Mostbutnotallinsomniaisthoughtto12otherhealthproblemsfromarthritisanddepressiontocardiovasculardisease.Thequestionofteniswhethertheinsomniacamefirstorwasaresultoftheotherdiseasesandhowtroublesleepingin13complicatesthoseotherproblems.Otherdiseases14theriskofinsomniaseemstoincreasewithageandtobemore15amongwomenespeciallyaftertheir50s.Smokingcaffeineandnumerous16drugsalsoaffectsleep. TheNIHisspendingabout$200millionthisyearonsleep-relatedresearchsome17tospecificdisordersandothers18theunderlyingscientificlawsthatcontrolthenervoussystemofsleep.Theagencywas19thepane’sreviewbeforedecidingwhatadditionalworkshouldbe20atinsomnia. 17

OneofthemostpressingchallengesthattheUnitedStates—andindeedtheworld—willfaceinthenextfewdecadesishowtoalleviatethegrowingstressthathumanactivitiesareplacingontheenvironment.Theconsequencesarejusttoogreattoignore.Wildlifehabitatsarebeingdegradedordisappearingaltogetherasnewdevelopmentstakeupmoreland.PlantandanimalspeciesarebecomingextinctatagreaterratenowthanatanytimeinEarth’shistory.Asmanyas30percentoftheworld’sfishstocksareoverexploited.Andthelistgoeson.Yetthereisreasontohavehopeforthefuture.Advancesincomputingpowerandmolecularbiologyareamongthetremendousincreasesinscientificcapabilitythatarehelpingresearchersgainabetterunderstandingoftheseproblems.Recentdevelopmentsinscienceandtechnologycouldprovidethebasisforsomemajorandtimelyactionsthatwouldimproveourunderstandingofhowhumanactivitiesaffecttheenvironment.Onepriorityforresearchisimprovinghydrologicalforecasting.Ithasbeenestimatedthattheworld’swaterusecouldtripleinthenexttwodecades.AlreadywidespreadwatershortageshaveoccurredinpartsofChinaIndiaNorthAfricaandtheArabianPeninsula.TheneedforwateralsoistakingitstollonfreshwaterecosystemsintheUnitedStates.Only2percentofthenation’sstreamsareconsideredingoodconditionandcloseto40percentofnativefishspeciesareraretoextinct.Usingavarietyofnewremotesensingtoolsscientistscanlearnmoreabouthowprecipitationaffectswaterlevelshowsurfacewaterisgeneratedandtransportedandhowchangesinthelandscapeaffectwatersupplies.Topreventoutbreaksofinfectiousdiseasesinplantsanimalsandhumansmorestudyisneededonhowpathogensparasitesanddisease-carryingspecies—aswellashumansandotherspeciestheyinfect—areaffectedbychangesintheenvironment.Theoveruseofantibioticsbothinhumansandinfarmanimalshascontributedtothegrowthofantibiotic-resistantmicroorganisms.Researcherscantakeadvantageofnewtechnologiesingeneticsandcomputingtobettermonitorandpredicttheeffectsthatenvironmentalchangesmighthaveondiseaseoutbreaks.HumanshavemadealterationstoEarth’ssurface—suchastropicaldeforestationreductionofsurfaceandgroundwaterandmassivedevelopment—sodramaticthattheyapproachthelevelsoftransformationthatoccurredduringglacialperiods.Suchalterationscausechangesinlocalandregionalclimateandwilldeterminethefutureofagriculture.Recentadvancesindatacollectionandanalysisshouldbeusedtodocumentandbetterunderstandthecausesandconsequencesofchangesinlandcoveranduse.Throughoutthetexttheauthormainlyemphasizes

Chronicinsomniaisamajorpublichealthproblem.Andtoomanypeopleareusing1therapiesevenwhilethereareafewtreatmentsthatdowork.MillionsofAmericans2awakeatnightcountingsheeporhaveastiffdrinkor3anpillhopingitwillmakethemsleepy.4expertsagreeallthatself-medicatingisabadideaandthecausesofchronicinsomniaremain5.a Chronicinsomniaisamajorpublichealthproblem.Andtoomanypeopleareusing1therapiesevenwhilethereareafewtreatmentsthatdowork.MillionsofAmericans2awakeatnightcountingsheeporhaveastiffdrinkor3anpillhopingitwillmakethemsleepy.4expertsagreeallthatself-medicatingisabadideaandthecausesofchronicinsomniaremain5. Almostathirdofadultshavetroublesleepingandabout10percenthave6ofdaytimeimpairmentthatsignaltrueinsomnia.But7thecomplaintsscientistsknowsurprisinglylittleaboutwhatcauseschronicinsomniaitshealthconsequencesandhowbesttotreatitapanelofspecialists8togetherbytheNationalInstitutesofHealthconcludedWednesday.Thepanelcalled9abroadrangeofresearchintoinsomnia10thatifscientistsunderstoodits11causestheycoulddevelopbettertreatments. Mostbutnotallinsomniaisthoughtto12otherhealthproblemsfromarthritisanddepressiontocardiovasculardisease.Thequestionofteniswhethertheinsomniacamefirstorwasaresultoftheotherdiseasesandhowtroublesleepingin13complicatesthoseotherproblems.Otherdiseases14theriskofinsomniaseemstoincreasewithageandtobemore15amongwomenespeciallyaftertheir50s.Smokingcaffeineandnumerous16drugsalsoaffectsleep. TheNIHisspendingabout$200millionthisyearonsleep-relatedresearchsome17tospecificdisordersandothers18theunderlyingscientificlawsthatcontrolthenervoussystemofsleep.Theagencywas19thepane’sreviewbeforedecidingwhatadditionalworkshouldbe20atinsomnia. 11

A是n阶矩阵且A3=0则______

设y=1+sinxx则=______

设二维随机变量XY在区域D://0＜x＜1|y|=x内服从均均分布求关于X的边缘概率密度函数及随机变量Z=2X+1的方差DZ

设fx为连续函数计算其中D是由y=x3y=1z=-1围成的区域

设A为n阶方阵A*为A的伴随矩阵且A11≠0证明方程组Ax=bb≠0有无穷多解的充要条件中b为A*X=0的解