已知（X,Y）的联合密度函数为f(x,y)大括号x^2+xy/3,0小于等于x小于等于1，0

(1)P(X>0.5)=∫dx∫(x^2+xy/3)dy =∫(2x^2+2x/3)dx =[(2/3)x^3+x^2/3]| =(2/3)(1-0.125)+(1/3)(1-0.25) =5/6. (2)P(x+ydx∫(x^2+xy/3)dy =∫[(1-x)x^2+x(1-x)^2/6]dx =(1/6)∫(x+4x^2-5x^3)dx =(1/6)(1/2+4/3-5