1-x²+2xy-y²
问题描述：
1-x²+2xy-y²
x²-y²+x-y
麻烦用因式分解解
答
1-x²+2xy-y²=1-(x-y)²=(1-x+y)(1+x-y)
x²-y²+x-y=(x-y)(x+y)+(x-y)=(x-y)(x+y+1)