x^2-y^2-2x+1
问题描述:
x^2-y^2-2x+1
4(x+y)^2-4(x+y)+1
答
x^2-y^2-2x+1
= (x^2 -2x +1) - y^2
= (x-1)^2 - y^2
=(x-1+y)(x-1-y)
4(x+y)^2-4(x+y)+1
=[2(x+y)-1]^2
=(2x+2y-1)^2