考研真题概率

1 F(Y)= p(Y & lt；y)=p(x^2<；Y)=p(-字根y；y & gt=1 ;0.5字根y+0.25字根y 1 >；y & gt=0

F(y)= F'(y)=0.375/根号y 1 & gt；y & gt=0;0.125/根号y ^ 4 >；y & gt=1;0其他人

2 cov(x,y)=cov(x,x^2)=ex^3-exex^2=

3 F(-0.5，4)= P(X & lt；-0.5，Y & lt4)= P(X & lt；-0.5,x^2<；4)= P(-2 & lt；X & lt-0.5)=0.4