已知x-3y=0,求（2x+y)/(x^2-2xy+y^2)*(x-y)的值
问题描述：
已知x-3y=0,求（2x+y)/(x^2-2xy+y^2)*(x-y)的值
已知x-3y=0,求（2x+y)/(x^2-2xy+y^2)*(x-y)的值
答
2x+y/x^2-2xy+y^2)*(x-y)=2x+y/(x-y)^2*(x-y)=2x+y/x-yx-3y=0.x=3y将x=3y带入2x+y/x-y=6y+y/3y-y=7/2（二分之七）