A is an [img=36x19]1803c4e61381e6b.png[/img] matrix and [img=12x14]1803c4e61b3a2fb.png[/img] is an n-dimensional column vector. If the [img=201x51]1803c4e628b33fd.png[/img], then the linear system ____________
A: [img=60x19]1803c4e6316cf85.png[/img] must have infinitly many solutions.
B: [img=139x51]1803c4e63cf2009.png[/img]must have nontrivial solutions.
C: [img=60x19]1803c4e6316cf85.png[/img] must have a unique solution.
D: [img=139x51]1803c4e63cf2009.png[/img] only has nontrivial solutions.
A: [img=60x19]1803c4e6316cf85.png[/img] must have infinitly many solutions.
B: [img=139x51]1803c4e63cf2009.png[/img]must have nontrivial solutions.
C: [img=60x19]1803c4e6316cf85.png[/img] must have a unique solution.
D: [img=139x51]1803c4e63cf2009.png[/img] only has nontrivial solutions.
B
举一反三
- Let A be a [img=41x19]1803c4e38325ee9.png[/img] matrix, then ________. A: If Ax=0 has only trivial solution, then Ax=b must have a unique solution. B: If Ax=0 has a nontrivial solution, then Ax=b must have infinitely many solutions. C: If Ax=b has a unique solution, then Ax=0 must have a unique solution. D: If Ax=0 has a nontrivial solution, then [img=55x23]1803c4e38c0c9df.png[/img] must have a nontrivial solution.
- 已知随机变量X的分布函数为[img=136x49]1803b69024c8270.png[/img] ，则X的均值和方差分别为 A: E(X)=2, D(X)=4 B: E(X)=4, D(x)=2 C: [img=162x43]1803b6902cd8bfb.png[/img] D: [img=162x43]1803b69034d9ffd.png[/img]
- 设[img=77x19]1802e2aa5a4095f.jpg[/img]，则E(X)=4，D(X)=4/3.
- 设随机变量[img=15x19]1803c5fbd2ccac8.png[/img]的期望E(X)=2，方差D(X)=4，随机变量[img=11x19]1803c5fbdae292b.png[/img]的期望E(Y)=4，方差D(Y)=9,E(XY)=10,则[img=33x23]1803c5fbe3431f2.png[/img]的相关系数[img=43x43]1803c5fbeab6ece.png[/img]。( )
- 随机变量X服从均匀分布[img=246x104]1803bbe29f8c799.png[/img]则E(X)=( ) A: 4 B: 4.5 C: 0.5 D: 1
内容
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随机变量X服从均匀分布[img=246x104]1803bbdf7304c7f.png[/img]则E(X)=( ) A: 4 B: 5 C: 0.5 D: 1
- 1
设随机变量(X,Y)在区域｛(x,y): 0<|y|< x <2｝内均匀分布，则以下结果正确的是 A: 当0<x<2时，[img=96x25]1802dded7db6eef.png[/img]. B: E(X)=4/3 C: 当0<|y|<2时,[img=105x45]1802dded872b92f.png[/img]. D: P(X<1)=0.5 E: 当0<x<2时,[img=110x45]1802dded915de6e.png[/img]. F: E(X)=2/3 G: 当0<y<2时，[img=95x43]1802dded9a54300.png[/img].
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设二维随机变量（X,Y) 的概率密度函数为[img=324x73]1803be452953729.jpg[/img], 则E(X)= . A: 1/2 B: 2/3 C: 3/4 D: 4/5
- 3
设二维随机变量（X,Y) 的概率密度函数为[img=324x73]1803be45e333af6.jpg[/img], 则E(X)= . A: 1/2 B: 2/3 C: 3/4 D: 4/5
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设[img=127x53]17f1b3d6db98b83.jpg[/img]，f（x）=arctanΧ，则[img=56x55]17f1b3d82842941.jpg[/img]=（）。 A: π B: 3π/4 C: -3π/4 D: 2π