WhenIcamethroughthecustomsattheairport,Ihadtopay________onaclockIhadbought.
二维随机变量(X,Y)在D=（x，y）0<y<1-x2上服从均匀分布，求Z1,Z2联合分布。
Thosewho’dliketovisittheexhibition________(sign)yournameshere.
________they'vegottoknoweachotheralittlebetter,theygetalongjustfine.
已知离散型随机变量X的概率分布为
X10203040
P a
(1)求常数a;(2)求X的数学期望EX.
