9(x-y)^2-6(y-x)^2+1
问题描述:
9(x-y)^2-6(y-x)^2+1
是9(x-y)^2-6(y-x)+1 打错了
答
9(x-y)^2-6(y-x)+1
=9(x-y)^2+6(x-y)+1
=[3(x-y)+1]^2
=(3x-3y+1)^2