- 问题详情:已知数列{an}满足an+1=λan+2n(n∈N*,λ∈R),且a1=2.(1)若λ=1,求数列{an}的通项公式;(2)若λ=2,*数列{}是等差数列,并求数列{an}的前n项和Sn.【回答】【考点】8H:数列递推式;8E:数列的求和.【分析】(1)当λ=1时,,由此利用累加法能求出数列{an}的通项公式.(2)当λ=2时, =,再由,能*数列{}是首...
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- 问题详情:已知等差数列{an}中,a7+a9=16,a4=1,则a12的值是( )A.64 B.31 C.30 D.15【回答】D知识点:数列题型:选择题...
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- 问题详情:已知等差数列{an}中,a6+a10=16,a4=1,则a12的值是A.15 B.30 C.31 D.64【回答】A知识点:数列题型:选择题...
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- 问题详情:观察下列各式:a+b=1,a2+b2=3,a3+b3=4,a4+b4=7,a5+b5=11,…,则a12+b12=A.521 B.322C.123 D.199【回答】B知识点:推理与*题型:选择题...
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- 问题详情:等差数列{an}满足:a4+a6+a8+a10+a12=20,则a9﹣=()A.1B.2C.3D.4【回答】B考点:等差数列的*质.专题:计算题;等差数列与等比数列.分析:在等差数列{an}中,由a4+a6+a8+a10+a12=20,能求出a8,再由a9﹣=(a8+d)﹣(a8+2d)=a8,能求出结果.解答:解:在等差数列{an}中,∵a4+a6+a8+a10+a12=5a8=20,∴a8=4,a9﹣=(a8+d)﹣(a8...
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- 问题详情:AndrewHolleman,a12-year-oldboy,lovedplayingintheopenlandnearhislandwaswetandforested,andmadeahomeforbirds,otheranimalsandmanydifferentplants. Itmadetheperfectplaceforhimtostudyandgettoknowthenature.Hehadseensomered-tailhawks,redfoxes,woodtur...
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- 问题详情:阅读理解AndrewHolleman,a12-year-oldboy,lovedplayingintheopenlandnearhishome.Thelandwaswetandforested,andmadeahomeforthebirds,otheranimalsandmanydifferentplants.Itmadetheperfectplaceforhimtostudyandgettoknowthenature.Hehadseensomered-tailedhawks,re...
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- 问题详情:水稻的体细胞中有12对染*体,也就是包含了()个DNA分子。A12 B24 C6 D32【回答】B知识点:基因控制生物的*状题型:选择题...
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- 问题详情:已知数列{an}为等差数列,且a1+a7+a13=4π,则tan(a2+a12)的值为()(A) (B)- (C)± (D)-【回答】B.因为a1+a7+a13=4π,所以a7=,tan(a2+a12)=tan=-,故选B.知识点:数列题型:选择题...
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- 问题详情:设等差数列{an}的前n项和为Sn,且a2+a7+a12=24,则S13=()A.52 B.78C.104 D.208【回答】C知识点:数列题型:选择题...
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- 问题详情:下列计算正确的是 A、a3•a4=a12 B、(a3)4=a7 C、(a2b)3=a6b3 D、【回答】C知识点:(补充)整式的除法题型:选择题...
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- 问题详情:下列运算中,结果正确的是(▲)A.a3•a4=a12 B.a10÷a2=a5 C.a2+a3=a5D.4a-5a=-a【回答】D 知识点:整式的乘法题型:未分类...
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- 问题详情:如图,正十二边形A1A2…A12,连接A3A7,A7A10,则∠A3A7A10=.【回答】75°.【分析】如图,作辅助线,首先*得=⊙O的周长,进而求得∠A3OA10==150°,运用圆周角定理问题即可解决.【解答】解:设该正十二边形的中心为O,如图,连接A10O和A3O,由题意知, =⊙O的周长,∴∠A3OA10==150°,∴∠A3A7A...
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- 问题详情:下列计算中,正确的是( ). A.a+a11=a12 B.5a-4a=a C.a6÷a5=1 D.(a2)3=a5 【回答】B;知识点:各地中考题型:选择题...
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- 问题详情:已知在等差数列{an}中,a7+a9=16,a4=1,则a12的值是A.15B.30 C.31D.64【回答】解析由等差数列的*质得a7+a9=a4+a12,因为a7+a9=16,a4=1,所以a12=15.故选A.*A知识点:数列题型:选择题...
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- 问题详情:完形填空XiaoQiang,a12-year-oldChineseboy,hastoomanyactivities.Hisfather 1_ himawayfromschoolfourafternoonsaweekanddriveshimacrosstowntopractice.“Idomostofmy 2 inthecarwhenweare_3 topractice,andIhavetodotherest(剩余的)whenIgeth...
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- 问题详情:设Sn是等差数列{an}的前n项和,a12=-8,S9=-9,则S16=( )A.-72 B.72 C.36 D.-36【回答】A【解析】由等差数列通项公式,前n项和公式可得知识点:数列题型:选择题...
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- 问题详情: AndrewHolleman,a12-year-oldboy,lovedplayingintheopenlandnearhislandwaswetandforested,andmadeahomeforbirds,otheranimalsandmanydifferentplants. Itmadetheperfectplaceforhimtostudyandgettoknowthenature.Hehadseensomered-tailhawks,redfoxes,woodt...
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- 问题详情:在正项等比数列{an}中,a1和a19为方程x2-10x+16=0的两根,则a8·a12=__________.【回答】16 知识点:数列题型:填空题...
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- 问题详情:已知Ba(AlO2)2可溶于水。右图表示的是向A12(SO4)3溶液中逐滴 加入Ba(OH)2溶液时,生成沉淀的物质的量y与加入Ba(OH)2的物质的量x的关系。下列有关叙述正确的是A.a-b时沉淀的物质的量:A1(OH)3比BaSO4多B.c-d时溶液中离子的物质的量...
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- 问题详情:(CNN)----A12-year-oldgirlwhohadafellingthatshemightbequitecleverhastakenatestandprovedshewasabsolutelyright.LydiaSebastianachievedthetopscoreof162onMensa,sCattellIIIBpaper,suggestingshehasahigherIQthanwell-knowngeniusesAlbertEinsteinandStephenHa...
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- 问题详情:用含有A12O3、SiO2和少量FeO·xFe2O3的铝灰制备A12(SO4)3·18H2O。,工艺流程如下(部分*作和条件略):Ⅰ.向铝灰中加入过量稀H2SO4,过滤:Ⅱ.向滤液中加入过量KMnO4溶液,调节溶液的pH约为3;Ⅲ.加热,产生大量棕*沉淀,静置,上层溶液呈紫红*:Ⅳ.加入MnSO4至紫红*消失,过滤;Ⅴ.浓缩、...
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- 问题详情:下列运算中正确的是( )A.a3-a2=a B.a3·a4=a12 C.a6÷a2=a3 D.(-a2)3=-a6【回答】D知识点:整式的乘法题型:选择题...
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- 问题详情:下列计算:(1)an•an=2an,(2)a6+a6=a12,(3)c•c5=c5,(4)26+26=27,(5)(3xy3)3=9x3y9中,正确的个数为()A.0个 B.1个 C.2个 D.3个【回答】B【考点】幂的乘方与积的乘方;合并同类项;同底数幂的乘法.【分析】根据同底数幂的乘法的*质,合并同类项的法则,积的乘方的*质,对各式分析判断后利用排除法...
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- 问题详情:A12-year-oldboynamedTimBrowngotlostinthemountains.However,hesurvivedatlastthankstohisamazingsurvival(生存,幸存)skills.OnedayinOctober2016,Tim wenthikingwithhisgroupintheMagaliesbergMountains,SouthAfrica.Atfirst,everythingwentwell.Butataboutone...
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