是不是(x^2-7x-6)(x^2+x-6)+12x^2,要是(x^2-7x-6)(x^2+x-6)-12x^2做不出来
(x^2-7x-6)(x^2+x-6)+12x^2
=x^4-7x^3-6x^2+x^3-7x^2-6x-6x^2+42x+36+12x^2
=x^4-6x^3-7x^2+36x+36
=x^2(x^2-6x-7)+36(x+1)
=x^2(x+1)(x-7)+36(x+1)
=(x+1)(x^3-7x^2+36)
=(x+1)(x^3-6x^2-x^2+6x-6x+36)
=(x+1)(x^2(x-6)-x(x-6)-6(x-6))
=(x+1)(x-6)(x^2-x-6)
=(x+1)(x-6)(x-3)(x+2)