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已知=(3,1),向量=(﹣4,﹣3),则向量=( )
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高一下学期数学《》真题及答案
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已知向量a=21b=x-2若a∥b则a+b等于
(-2,-1)
(2,1)
(3,-1)
(-3,1)
已知向量a=31b=13c=k7若a-c∥b则k=
已知向量a=-31b=1-2若-2a+b⊥ka+b则实数k=.
已知点A01B32向量=
(﹣3,﹣1)
(﹣3,1)
(3,﹣1)
(3,1)
已知向量a=12b=31那么|2a+3b|=.
已知四维列向量α1α2α3线性无关若向量βii=1234是非零向量且与向量α1α2α3均正交则向量组
1
2
3
4
已知向量a=21b=x-2若a∥b则a+b等于
(-2,-1)
(2,1)
(3,-1)
(-3,1)
已知向量a=31b=若a+λb与a垂直则λ等于________.
已知向量组Ⅰα1α2Ⅱα1α2α3Ⅲα1α2α4.如果各向量组的秩分别为rⅠ=rⅡ=2rⅢ=3则向量
1.
2.
3.
不能确定.
若平面αβ的法向量分别为n1=235n2=-31-4则
α∥β
α⊥β
α、β相交但不垂直
以上均不正确
已知向量组Ⅰα1α2α3Ⅱα1α2α3α4Ⅲα1α2α3α5如果各向量组的秩分别为rⅠ=rⅡ=3rⅢ
已知向量=31=﹣2则下列向量可以与垂直的是
(﹣1,2)
(2,﹣1)
(4,2)
(﹣4,2)
已知向量a=31b=2λ.若a∥b则实数λ=.
已知向量=1λ=31若向量2﹣与=12共线则向量在向量方向上的投影为.
已知向量a=21b=-13若存在向量c使得a·c=4b·c=-9则向量c=.
已知向量a=-34向量b∥a且|b|=1那么b=.
已知向量=1λ=31若向量2﹣与=12共线则向量在向量方向上的投影为.
已知点A.1-2若点A.B.的中点坐标为31且与向量a=1λ共线则λ=________.
已知向量a=43b=-12.若向量a-λb与2a+b垂直则λ=.
已知向量=31=24则向量=
(5,5)
(6,4)
(﹣1,3)
(1,﹣3)
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There'snodoubt﹣thatlearningaforeignlanguageisdifficultandwhenitcomestospeakinginthelanguageitcanberatherterrifying.Irememberwalkingintomyfirst﹣everSpanishclassatuniversityonlytodiscoverthathalfofmyclassmateswerealreadyfluentinseverallanguages.1 AtfirstthethoughtofspeakinginSpanishterrifiedme;notonlyweremyvocabularyandgrammarverylimitedbutIhadneverspokenanotherlanguagebefore.ButIwasdeterminedtoovercomemyfearandbyemployingafewsimplestrategies策略Ihavebeenabletobuildmyconfidenceanddevelopatmyownpace.2 FirstlyrememberitisOKtomakemistakesandthatyoushouldfacethem3Butwhenitcomestolanguagelearningweoftenaimforperfectionandfeelasthoughwearenotreadytospeakuntilwehaveenoughwordsorgrammaticalknowledge.Thetruthisthatyouwillneverfeelreadyandinsteaditisimportanttousetheknowledgethatyoudohavetocommunicatewhatyoucan. Thisleadsontomynexttip:4Thiscanbeahardoneespeciallyifyouareinalargelanguageclass.Itisimportanttorememberthatwealllearnatdifferentspeedsandthroughdifferentstylesoflearning.Byallmeanskeepupwithyourclassmaterialbutdonotworryifyoudon'tunderstandeverything﹣especiallyintheearlystages. Lastlycelebratethesmallsuccessesandrememberhowfaryouhavecome!5Soinsteadoffocusingonhowforyouhavetogofocusontheprogressyouhavealreadymadeandbeproudofyourachievements! A.Thissoundsobvious. B.It'shardlydifficulttodoso. C.Ifeltitwasreallyoutofmyreach. D.Don'tcompareyourselfwithothers. E.Trytokeepupwithotherclassmates. F.Afteralleverytinysuccessandlittleprogressisworthcheeringfor. G.SoIwillshareafewtipswithyouhopingthatyoufindthemusefultoo.
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把下列数据用科学记数法表示出来全世界人口约为61亿
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LONDON﹣BritainpreparesforavoteThursdaythatwilldecidewhetheritleavestheEuropeanUnion.Thedebatehascenteredonimmigrationandeconomicsecurity.Bothsideshaveloweredthetoneoftheirargumentsafterathree﹣daysuspension暂停ofcampaigningthatfollowedthemurderofananti﹣Brexitlawmakeranincidentthatpolls民意调查suggesthasshockedmanypreviouslyundecidedvoterswhonowsaytheywillvotetoremain. TheseareuncertaintimesinanationwhoseeconomyisthesecondlargestintheEuropeanUnion.Therisksarehuge.Therearewarningsthatleavingthe28﹣membergroupmaycausetheBritishpoundtolose15percentofitsvalueandbringtheresignation辞职ofDavidCameronthecountry'sprimeminister;hisstayornotdependsonwhetherBritainlistenstohimandvotestoremain. FormonthstheLeavecampaignhasbeenhittingthestreets.Itsargumentsarebasedlargelyon immigrationandthebeliefthatBritainhashandedcontrolofitsborders边界toaEuropeansuperstate:TheU.K.haslostcontrolovermigration.WehavetoacceptanyoneintothiscountryiftheyhaveanEUpassportnomatteriftheyhaveacriminalrecordornot.Wearenotallowedtosay'no'topeopleandthatisdamagingforthesecurityoftheU.K.butitisalsoputtingpressureonjobsandopportunitiesforyoungpeoplesaidTomHarwoodaBrexitcampaigner. ThemurderofJoCoxananti﹣Brexitpro﹣immigrantlawmakerbyafarrightextremist极端分子withahistoryofmentalproblemshadaseriouseffectonbothcampaignsandonvoters. PollssincetheJune16thmurdershowedtheLeavecamplosinggroundbutwithbothsidesstillverycloseonareferendum全民投票thatmanybelievecouldchangethecourseofEuropeanhistory. 1WhatdoestheunderlinedwordBrexitinparagraph3mean?. A.BreakthelawoftheEuropeanUnion. B.BreakawayfromtheEuropeanUnion. C.BuildtheexittotheEuropeanUnion. D.BantheimmigrationintoBritain. 2Whatisimpliedfromthepassage? A.TheimmigrationhascausedgreatconcerninBritain. B.BrexitwillbegoodforBritisheconomy. C.Bothcampshavebeencampaigninganddebatingonthestreetsformonths. D.ThemurderofJoCoxmademanyvotersdeterminedtovotefortheexit. 3Whichofthefollowingstatementistrue? A.BritainwillleavetheEuropeanUnionafterthevote. B.AnyonewithapassportcanchoosetostayandworkinBritain. C.WhetherCameronwillresigndependsontheresultofthereferendum. D.JoCoxwasmurderedbyaBrexitcampaignerinJune16m. 4What'stheattitudeofthereporttotheeventofBrexit? A.Positive B.Negative C.Indifferent漠不关心的 D.Concerned
Myfirstlessonwasatameeting.AswesettledaroundthetableIheardMegwhowas1arecentoperationtalkingtoJudiththemanagerofourprojectThankyousomuchfor2mydaughterstotheirdancelessonlastweek.Don'tmentionitJudithsaidItwasnothing. Knowinghow3JudithwaswithherworkkidsandagingparentsIfoundherdrivingMeg'schildrentodancelessonsunbelievably4. IwasabouttosaymoreaboutthiswhenDonnaanothercolleagueenteredtheroom5. Sheapologizedforbeinglatesayingshejusthadhostedalunchforherfriendswhowereoverseventy.ThatwassoniceofyouIsaid6howshedidn'tliketocookorclean.Ohshesaidwavingher7Itwasnothing.SomehowIcouldstilltellthe8inhervoice.Shegainedasenseofsatisfactionfromtheentertainment款待offeredtoherfriends. Seeingtheir9tohelpothersselflesslyIstartedthinkingabouttheconceptofnothingthispeacefulandgenerouswayofliving﹣﹣﹣wasitreallynothingorweretheysimplysayingthat?Isuddenly10thatonceIspentawholeafternoonafterworkhelpingafriend11aspeechshewasgoingtodeliver.I12hertorearrange重新安排theorderofthestoriesinthelecturetomakeitsoundmore13.Afterthefifthtryshefinally14it.Shehuggedmewith15sayingthankstome.Ismiledandsaiditwasnothing. SuddenlyIrealizedthathelpingsomeonewasreallysomethingtome.Ilearntthatgivingfromtheheartdoesn't16meanhardwork.The17isfindingsomethingwelovetodoandfindingsomeonewho18thatsomething.Ourgenerositycan19othersaswellasourselves.Onceyouhaveagood20ofitit'snothing.Andit'sreallysomething. 1A.recoveringfrom B.adaptingto C.goingthrough D.joiningin 2A.guiding B.fetching C.driving D.dragging 3A.common B.busy C.strange D.practical 4A.frightened B.sincere C.gifted D.generous 5A.hurriedly B.disappointedly C.angrily D.unexpectedly 6A.ignoring B.knowing C.forgetting D.predicting 7A.eyes B.feet C.leg D.hand 8A.pleasure B.sadness C.surprise D.regret 9A.progress B.adventure C.promise D.willingness 10A.referred B.refused C.remembered D.respected 11A.preparefor B.putup C.giveaway D.takeapart 12A.begged B.invited C.advised D.permitted 13A.unbelievable B.reasonable C.sensitive D.puzzling 14A.got B.meant C.caught D.made 15A.concern B.worry C.gratitude D.apology 16A.normally B.accidentally C.necessarily D.possibly 17A.treat B.trick C.belief D.plan 18A.needs B.admires C.loves D.defends 19A.defeat B.benefit C.win D.regard 20A.order B.balance C.impression D.command
Fishingisapopularactivityandeveryfishermanknowstherule:Keepthebigonesthrowthesmalleronesback.Theideabehinditissimple﹣thelargerfishareprobablyolder.Ifyoukeepthesmalleronestheywon'tbeabletoreproduceandthefishpopulationwillbeindanger. Butfishingoutthelargestfishfromapopulationhasanunwantedeffect:Overtimefeweradultfishgetreallybig.Ifonlythesmallerfishreproducethenfuturegenerationswillbecomesmaller.Thisisanexampleofevolution进化inaction. OnescientistDr.DavidConoverhasspentthelastdecadestudyingtheeffectsofthekeepthebigonesruleandiftheycanbechanged. TosetuphisexperimentConoverandhisteamcaughthundredsofsilversidefishanddividedthemintosixgroups.FortwogroupsConoverfollowedtheukeepthelargeonesruleandtookoutthebiggestfish.Fortwoothergroupsheremovedonlythesmallfish.Forthelasttwogroupsheremovedfishatrandom随意的. Afterfiveyearshemeasuredthefishineachgroup.Inthetwogroupswherethelargestfishwereregularlyremovedtheaveragefishsizewassmallerthantheaveragesizeintheothergroups.Herewastheevolutioninaction:Ifonlysmallfishsurvivetoreproducethenfuturegenerationsoffishwillalsotendtobesmall. ForthesecondfiveyearsofhisexperimentConoverchangedtherulesandtookfishrandomlyfromeachgroup.Attheendoftheexperimenthefoundthatthefishthatwereinthekeepthelargeonesgroupforthefirstfiveyearshadstartedtogetlargeragainalthoughhecalculateditwouldtakeatleast12yearsforthefishinthatgrouptoreturntotheiroriginalsize. Inotherwordsittakeslesstimetoshrinkthanitdoestorecover. 1What'sthetraditionalruleinfishing? A.Keepbothbigandsmallones. B.Keepbigonesandfreesmallones. C.Keepsmallonesandthrowbigonesback. D.Keeptheonesthatcanreproduce. 2DavidConoverdidexperimentonfishinginorderto. A.findpracticalrulesinfishing B.provethetraditionalfishingrulewasreasonable C.seekforgoodfishestoreproduce D.findgoodmethodinraisingsilversidefish 3WhatdidDavidConoversexperimentprove? A.Fishermanshouldfishatcertaintime. B.Fishermanshouldkeepbigonesandfreesmallone. C.Fishermanshouldkeepsmallonesandthrowbigonesback. D.Fishermanshouldkeepfishatrandom. 4Whatdoestheunderlinedwordshrinkmeaninthelastparagraph? A.Becomesmaller. B.Becomeill. C.Becomeweaker. D.Becomeless.
上周这家餐馆决定雇佣名厨以便能赢回顾客.sothat
ThefirstMondayinSeptemberisLaborDayintheUnitedStates.Thenationalholidaybeganmorethan100yearsago1honorlow﹣paidfactoryworkers. LaborDayalso2informalmarkstheendofsummer.ManystudentsreturntoschoolafterLaborDay.Thehotdaysofsummerturn3cool.ManyAmericanscelebratetheholiday4anoutdoorfamilybarbecue. ButLaborDaystartedwithastruggle.OnMay1st1889workersdemonstrated游行onthestreetsofParisFrance.InternationalLaborDaywasborn.Mostindustrialized5countryintheworld﹣excepttheUnited StatesandCanada﹣﹣celebrateLaborDayonthefirstofMay. ThefirstAmericanLaborDaycelebration6holdonSeptember5th1882inNewYorkCity.About10000workersmarchedthroughthestreetstoshowthe7strongoflabororganizations. FormanyyearsafterthatAmericanworkersusedthefirstMondayinSeptembertodemandbetterworkingconditionsandpay.Musicwasapartofmanyofthosemarchesandmanylaborsongstraditionallytellstoriesofconflictandhopesfor8betterlife.HereareWeShallNotBeMoved.WhichSideAreYouOn?BreadandRoses. EventhoughLaborDaydemonstrationsarenot9commonastheyareintheU.S.thesongremindsustocelebratetheeffortandlovethatmanypeoplegiveto10theywork.
假定你是晨光中学的李华来自英国CaterhamSchool的一批学生来你校与同学们开展了为期一周的文化交流活动.请你给校园英文报写一篇报道.内容包括: 1.活动时间:6月24日一6月30日; 2.活动内容:如画作展出音乐表演等; 3.活动意义. 注意: 1.词数80左右题目已为你写好; 2.可适当增加细节以使行文连贯. CulturalExchangebetweenCaterhamSchoolandChenguangHighSchool
下列与物质运输有关的叙述错误的是
以下有关实验的叙述错误的是
美国白蛾是一种严重危害果林木农作物的食叶性害虫自入侵以来对我国多个省市造成了严重危害.周氏啮小蜂能将产卵器刺入美国白蛾等害虫坚硬的蛹表皮将卵产在蛹内并在蛹内发育成长吸尽蛹中全部营养从而杀死美国白蛾等害虫.核型多角体病毒HcNPV可以通过侵染美国白蛾幼虫使其部分死亡. 1在生态系统组成成分中美国白蛾属于HcNPV与美国白蛾的种间关系是. 2科研人员分别对放蜂区按比例释放一定数量的周氏啮小蜂不用农药和对照区常规农药防治美国白蛾蛹被周氏啮小蜂和其他天敌寄生的情况进行了调查结果如下图 统计数据发现放蜂区其他天敌对美国白蛾蛹的寄生率升高可能原因是. 3为取得更好的防治效果科研人员计划使用HcNPV和周氏啮小蜂共同防蛾.假设“带毒蛹”被HcNPV感染的虫蛹对周氏啮小蜂的繁殖没有影响.为验证该假设设计了如下实验方案.请在下列选项中选择a~f填入①~④处选择g~i填入⑤处. a.“带毒”美国白蛾成虫b.“带毒”美国白蛾蛹 c.“不带毒”美国白蛾成虫d.“不带毒”美国白蛾蛹 e.HcNPV病毒f.周氏啮小蜂g.总出蜂量h.雌蜂量i.雌雄蜂寿命 若实验结果为则二者可以共同用于同一区域美国白蛾的防治.
Youmayfinditexcitingtogetapart﹣timejobduringthesummervacation.1Whenyougetaninvitationtoajobinterviewyouarehalfwaytowardsyourgoal﹣﹣ajoboffer.Hereareafewthingsyoushoulddoafterwards. Respondtotheinvitationtotheinterview.Thankthesenderfortheirtimeandfortheopportunitytoorganizetheinterviewconfirmingthatyouwillbeavailableatthedeterminedtime.2. 3Youneedtodosomeresearchonthecompanyandlearnasmuchaboutthecompanyaspossiblebeforetheinterview.Usethecompany'swebsiteandnewspaperarticlestogatherasmuchinformationaspossible.Youshouldalsobereadytotalkindepthaboutthecompanyandthepositionyouareapplyingfor. 4It'sbesttoprepareforawidevarietyofquestionsbythinkingaboutyourowncareergoalsandsoon.Wheredoyouseeyourselfinfiveyears?isacommonquestion.Workingdiligentlyforyouofcourse!Butunlessyouareactuallytryingtogetajobinyourchosencareerthisprobablyisn'tagoodanswer. Practicewithafriend.5Notonlywillthisgiveyouawaytostructureyourpreparationbutitwillalsohelpyougetcomfortablewithgivinganswers.Practicegivingconcisecompleteanswersandmaintainingeyecontactwiththeinterviewerswhileyougivethem. A.Askpeoplearoundyouforhelp. B.Ifyouhaveafriendwhoisalsopreparingforaninterviewconsiderpreparingtogether. C.Ifyouneedmoreinformationabouttheinterviewthisisthetimetoask. D.Butdoyouknowhowtoprepareforajobinterview? E.Thinkaboutquestionstheinterviewerislikelytoask. F.Whatarethechancesforprofessionalgrowthinthisjobopportunity. G.Doyourhomework.
利用科学记数法表示的数原来各是什么数2×105=
Ittakesabigbrain﹣ahumanbrain﹣todomath.Orsoyoumightthink.Butscientistshavefoundthatotheranimalssuchaschimpanzeesmonkeysandevenpigeonscandosomeadditionandsubtraction减法.Nownewresearchshowsthathoneybees﹣withbrainsthesizeofsesameseeds﹣candobasicmath. Researchersputhoneybeesthrough100trialstotrainthemtoaddandsubtract.TheyfirstputthebeesinaY﹣shapedmaze迷宫andpresentedthemwithacertainnumberofeitheryelloworblueshapes.Yellowshowedthebeesshouldsubtractwhilebluemeanttheyshouldadd. Thebeesthenenteredthedecisionroomwheretheywerepresentedwithacorrectanswerononesideandanincorrectanswerontheotherside.Iftheypickedtherightanswertheywererewardedwithasugarydrink.Ifnottheygotbitterwater.Theresearchersalsoputthebeesthroughanothertesttrialwithoutarewardorpunishmenttomakesurethereweren'tanysmellmarksinfluencingthebees'choices. Atfirstthebeespickedanswersrandomly随意地.Youseethattheabilityofthebeestodoitstartsataboutchancelevel50%showingusthebeesarejustchoosingatrandom.Overtimetheirabilitycomesuptoabout80%sotheyactuallystarttoperformquitewell. ScarlettHowardoneofthestudyauthorsandaresearcheratPaulSabatierUniversityinFrancesaysthebeeswereevenabletoaddandsubtractcorrectlywhenpresentedwithanumbertheyhadneverseenbefore.ThestudyisinthejournalScienceAdvances.Thingslikethisletusknowthere'realotofmysteriestobeexploredthereandtheirbrainsmightnotbeassimplisticasweoncethought.Howardadded. 1thetesttrialonhoneybeeswithoutarewardorpunishmentwasdone. A.tohelpimprovetheircalculatingskills B.toavoidsmells'influenceontheirchoices C.toshowtheimportanceofarewardtothem D.toincreasethechanceleveloftheircorrectanswers 2Whatcanbelearnedfromthelastparagraph? A.Honeybeescanonlyworkoutnumberstaughtbefore. B.Alotofmysteriesabouthoneybeeshavebeensolved. C.Thebrainsizeofhoneybeesdeterminestheircalculatingability. D.Thepowerofhoneybeesbrainsmaygobeyondourexpectations. 3Whatistheauthor'spurposeinwritingthetext? A.Topresenthoneybees'abilitytoperformbasicmath. B.Topersuadepeopletoexploremoreabouthoneybees. C.Todiscusshowhoneybeesrecognizeunfamiliarnumbers. D.Toexplainwhyhoneybeesaresmarterthanotheranimals.
假定你是李华你在某贴吧上看到美国孔子学院ConfuciusInstitute的学生Henry发帖希望通过网络视频互动学习中国诗词.请你给他写封邮件内容包括: 1.表示愿意帮助他; 2.说明你想帮助他的原因. 注意: 1.词数100左右; 2.可以适当增加细节以使行文连贯.
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