D(z)=100D(x)D(x)=D(z)/100pxy=0.8cov(x,y)=0.8√D(x)D(y)cov(y,z)=10cov(y,x)=10cov(x,y)=8√D(x)D(y)=0.8√D(z)D(y)pyz=cov(y,z)/√D(z)D(y)=0.8如有意见，欢迎讨论，共同学习；如有帮助，请选为满意回答！
