原式=(36x²+84x+49)(3x²+7x+4)-6令a=3x²+7x+4则36x²+84x+49=12a+1原式=a(12a+1)-6=12a²+a-6=(3a-2)(4a+3)=(9x²+21x+10)(12x²+28x+19)=(3x+2)(3x+5)(12x²+28x+19)