x^2-y^2-1+2y因式分解,

题目

x^2-y^2-1+2y因式分解,
-x^2-y^2+1-2xy因式分解

答案

x²-y²-1+2y
=x²-(y²-2y+1)
=x²-(y-1)²
=(x+y-1)(x-y+1)
-x²-y²+1-2xy
=1-(x²+2xy+y²)
=1-(x+y)²
=(1+x+y)(1-x-y)