Question

分解因式(x²+y²-1)²-4x²y²

Answer 1

(x²+y²-1)²-4x²y²
=（x²+y²-1-2xy ）(x²+y²-1+2xy )
= （(x-y)²-1）（（x+y）²-1）
=（x-y+1）(x-y-1)(x+y+1)(x+y-1)

Answer 2

原式=（x^2+y^2-1+2xy)(x^2+y^2-1-2xy)
=[(x+y)^2-1][(x-y)^2-1]
=(x+y+1)(x+y-1)(x-y+1)(x-y-1)