把（x2+2x-2)(x2-4x-2)+5x2因式分解
问题描述：
把（x2+2x-2)(x2-4x-2)+5x2因式分解
答
设y=x^2-3x-2,
(x^2+2x-2)(x^2-4x-2)+5x^2
=(y+5x)(y-x)+5x^2
=y^2+4xy-5x^2+5x^2
=y^2+4xy
=y(y+4x)
=(x^2-3x-2)(x^2+x-2)
=(x^2-3x-2)(x-1)(x+2)