X射线的波长范围是（）
A: [img=182x33]18034993b4d71e4.png[/img]
B: [img=134x25]18034993bdfdf0e.png[/img]
C: [img=171x24]18034993c655b18.png[/img]
D: [img=182x26]18034993d43bcaa.png[/img]
A: [img=182x33]18034993b4d71e4.png[/img]
B: [img=134x25]18034993bdfdf0e.png[/img]
C: [img=171x24]18034993c655b18.png[/img]
D: [img=182x26]18034993d43bcaa.png[/img]
举一反三
- 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]
- Which of the following propositions is false,set A = {x,x is an integer and[img=60x23]1803a1c6eebb7a3.png[/img]} ? ( ) A: [img=113x25]1803a1c6f77ce06.png[/img] B: [img=139x25]1803a1c7001fe79.png[/img] C: [img=51x22]1803a1c70863f61.png[/img] D: {x|x is an integer and |x| 4}[img=33x22]1803a1c711a7c63.png[/img]
- Which of the following propositions is false,set A = {x,x is an integer and [img=60x23]1803a1c503ffa04.png[/img]} ? ( ) A: [img=113x25]1803a1c50cc3162.png[/img] B: [img=139x25]1803a1c514e60ea.png[/img] C: [img=51x22]1803a1c51dd52ef.png[/img] D: {x|x is an integer and |x| <4} [img=33x22]1803a1c525cf1bd.png[/img]
- 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F(x)和G(x)都是f(x)的原函数，则下式一定成立的有（） A: [img=134x25]1803445933678cc.png[/img] B: [img=99x25]180344593bc49d6.png[/img] C: [img=134x25]18034459436fa2a.png[/img] D: [img=178x47]180344594c44648.png[/img]