若(x+y)(x-y)^2-xy(x+y)=A(x+y),则A=什么
问题描述:
若(x+y)(x-y)^2-xy(x+y)=A(x+y),则A=什么
答
(x+y)(x-y)^2-xy(x+y)
原式=(x+y)[(x-y)^2-xy]
=(x+y)(x^2+y^2-3xy)
所以A=x^2+y^2-3xy