(x²+x+1)(x²+x+2)-12    把x²+x看作一个整体

=？       详细步骤

设x^2+x=y

（y+1）（y+2）-12

=y^2+3y-10

=(y+5)(y-2)

=(x^2+x+5)(x^2+x-2)

=(x^2+x+5)(x+2)(x-1)