(x+6)(x+3)(x-1)(x-2)+3x²
=(x+6)(x-1)(x+3)(x-2)+3x²
=(x²+5x-6)(x²+x-6)+3x²
=(x²+x-6)²+4x(x²+x-6)+3x²
=(x²+x-6+3x)(x²+x-6+x)
=(x²+4x-6)(x²+2x-6)
=[(x+2)²-10][(x+1)²-7]
=(x+2+√10)(x+2-√10)(x+1+√7)(x+1-√7)
原式=(x+6)(x-1)(x+3)(x-2)
=(x*2-6+5x)(x*2-6+x)
把x*2-6作为一个整体