（x+2)(x+4)(x+6)(x+12)+3x^2
=（x+2)(x+12)(x+4)(x+6)+3x^2
=（x^2+14x+24)(x^2+10x+24)+3x^2
=[(x^2+10x+24)+4x](x^2+10x+24)+3x^2
=(x^2+10x+24)^2+4x(x^2+10x+24)+3x^2
=(x^2+10x+24+3x)(x^2+10x+24+x)
=(x^2+13x+24)(x^2+11x+24)