Fz(z)=P(Z=z)=1-∫(1/2~1)(1/y~2) f(x,y)dxdy
f=F'
P(A|B)=P(A|B非)
所以A的發(fā)生概率和B無(wú)關(guān)
P(AB非)=P(A)P(B非)=0.4*(1-0.5)=0.2請(qǐng)您把過(guò)程詳細(xì)化。畫(huà)個(gè)xy=z的曲線(xiàn)，還有矩形，看出積分范圍，這個(gè)積分是xy>z的，所以是1-Fz(z)=1-∫(1/2~1)∫(z/y~2) 1/2 dxdy=1- ∫(z/2~1) (1-z/2y) dy = 1-{(y-(z/2)lny)|(z/2~1)}=1-{z/2-(z/2)ln(z/2)-1+0) =2-(z/2)(1-ln(z/2)) fz(z)=F'z(z)=-(z/2)(-1/(z/2))-(1-ln(z/2))/2 =1-1/2+ln(z/2)/2=1/2+0.5ln(0.5z) (0