若X-Y分之X+2Y等于2,则代数式X-Y分之2(X+2Y)-X+2Y分之4(X-Y)的值为
问题描述:
若X-Y分之X+2Y等于2,则代数式X-Y分之2(X+2Y)-X+2Y分之4(X-Y)的值为
答
(x+2y)/(x-y)=2
取倒数
(x-y)/(x+2y)=1/2
所以2(x+2y)/(x-y)-4(x-y)/(x+2y)
=2×2-4×1/2
=2