[单选题]设α是直线l的斜角,向量a=(-1,2),b=(sinα,cosα+2sinα),若a⊥b,则直线l的斜率是A、B、-C、D、-
[单选题]直线x-y+m=0与圆x2+y2-2x-1=0有两个不同交点的一个充分不必要条件是 []A.-3<m<1B.-4<m<2C.0<m<1D.m<1
[单选题]“x<-1”是“x2-1>0”的( )A.充要条件B.必要而不充分条件C.充分而不必要条件D.既不充分也不必要
[单选题]已知α,β,γ为互不重合的三个平面,命题p:若β⊥γ,β⊥γ,则α∥γ;命题q:若α上不共线的三点到β的距离相等,则α∥β.对以上两个命题,下列结论中正确的是[ ]A.命题“p且q”为真B.命题“p或q”为假C.命题“p或q”为假D.命题“p且q”为假
[单选题]给出下列命题:(1)两个具有公共终点的向量,一定是共线向量.(2)两个向量不能比较大小,但它们的模能比较大小.(3)a=0(为实数),则必为零.(4),为实数,若a=b,则a与b共线.其中错误的命题的个数为?A.1B.2C.3D.4
[单选题]Some animals ______ the tiger, the lion and the wolf are meat-eaters. [ ]A. such like B. such as C. for example D. including
[单选题]如图,已知点O是边长为1的等边△A.C的中心,则(0A+OB)(0A+0C)等于B[ ]A.B.C.D.
[单选题]已知p:-<a<元2,g: f(x)=log na x在(02+∞)内是增函数,则p是q的( )A.充分不必要条件B.必要不充分条件C.充要条件D.既不充分也不必要条件
[单选题]已知,A(–3, 1)、B(2, –4),则直线AB上方向向量AB的坐标是( )A.(–5, 5) B.(–1, –3)C.(5, –5)D.(–3, –1)
[单选题]A.ter three weeks adjustment to the new environment, he managed to accustom himself to be more _____with people. [ ]A. in reliefB. at easeC. in peace D. at stake
[单选题]下列命题中真命题是( )A.命题“存在x∈R.x2-x-2≥0”的否定是:“不存在x∈R.x2-x-2<0”.B.线性回归直线bX恒过样本中心(元可),且至少过一个样本点. C.存在x∈02,使sin x+ cosx3.D.函数f(x)=x351x2的零点在区间2内.
[单选题]The Chinese language differs from Western languages ______, instead of an alphabet, it uses characterswhich _______ ideas, objects or deeds . [ ]A. for which; take forB. in that; stand for C. in which; make forD. on that; wish for
[单选题]在集合{1,2,3,4}中任取一个偶数a和一个奇数b构成以原点为起点的向量α=(a,b).从所有得到的以原点为起点的向量中任取两个向量为邻边作三角形,事件“所得三角形的面积等于1”的概率为 ( )A.6B.3C.2D.2-3
[单选题]原命题:“a 、b 、c ∈R ,若a>b ,则ac2>bc2”以及它的逆命题、否命题、逆否命题中,真命题共有?[ ]A.0 个B.1 个C.2 个D.4 个
[单选题]Living with a host family while studying abroad, in which there may be some other college students, __________ you the chance to learn more about the new culture.A.giveB.givesC.givingD.to give
[计算题](本小题满分14分)给定两个长度为1的平面向量OA和OB,它们的夹角为120°.如图所示,点C在以O为圆心的圆弧HB上变动.若OC=xoA+ vOB,其中x,y?R,试求x+y的最大值.BOA
[计算题]写出下列命题的否定,并判断其真假.(1)P:xR.x2-x+2≥0(2)q:所有的正方形都是矩形;(3)p:x∈R,x2+2x+2≤0;(4)至少有一个实数x,使得x3+1=0
[单选题]已知命题p:x∈R:2x2-2x+3>0,则A.p:x∈R2x2-2x+3≤0B.p:3x0∈R,x22x+3≤0C.→p:3x∈R2x0-2x0+3>0D.p:x∈R2x2-2x+3≥0
[单选题]Sam _____ some knowledge of the computer just by watching others working on it.?A.brought upB.put upC.set upD.picked up
[单选题]“”是“”的[ ]A.必要非充分条件B.充分非必要条件C.分必要条件D.既非充分又非必要条件
[单选题]“x>0”是“x≠0”的[ ]A.充分而不必要条件B.必要而不充分条件C.充分必要条件D.既不充分也不必要条件