Since [img=98x47]1803e24ffc0cd5f.png[/img] is not defined at [img=44x18]1803e25004aea21.png[/img]，[img=62x33]1803e2500d5e374.png[/img] does not exist.
举一反三
- 3. Let [img=161x53]1802dde8d59661c.png[/img] and [img=180x61]1802dde8df7d956.png[/img].Determine whether [img=62x33]1802dde8e7e5fb9.png[/img] and [img=61x33]1802dde8f088425.png[/img] exist or not. A: (A) [img=62x33]1802dde8f81f6da.png[/img] and [img=61x33]1802dde8ff2f966.png[/img] both exist. B: (B) [img=62x33]1802dde8f81f6da.png[/img] exists but [img=61x33]1802dde8ff2f966.png[/img] does not exist. C: (C) [img=62x33]1802dde8f81f6da.png[/img] does not exist but [img=61x33]1802dde8ff2f966.png[/img] exists. D: (D) [img=62x33]1802dde8f81f6da.png[/img] and [img=61x33]1802dde8ff2f966.png[/img] do not exist.
- 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].
- 设X为随机变量，若数学期望E(X)存在，则数学期望E(E(X))=__________。 A: E(X) B: 0 C: [img=51x27]18038f919d83a08.png[/img] D: [img=63x27]18038f91a6f0476.png[/img]
- True or False : If [img=52x32]1802ddd740eab2f.png[/img] does not exist and [img=51x32]1802ddd748fbd7e.png[/img] does not exist either, then [img=94x33]1802ddd750d8d30.png[/img] does not exist. A: True. B: False. C: - D: -
- 在下列命题中:如果f(x)=[img=28x44]17e0bf9914bb2f1.png[/img],那么[img=27x29]17e0bf97582597b.png[/img]f(x)=0;如果f(x)=[img=28x44]17e0bf992111a1c.png[/img],那么[img=27x29]17e0bf97582597b.png[/img]f(x)=0;如果f(x)=[img=55x44]17e0bf992d8de0a.png[/img],那么[img=29x29]17e0bf9939482bb.png[/img]f(x)不存在;如果f(x)=[img=87x53]17e0bf99450fa82.png[/img],那么[img=27x29]17e0bf97582597b.png[/img]f(x)=0。其中错误命题的个数是( A: 0 B: 1 C: 2 D: 3