(1)原式= 1 8 (x4-16)= 1 8 (x2+4)(x+2)(x-2);(2)原式=3(x2-6x+9)=3(x-3)2;(3)原式=2(n-m)2[3a+4(n-m)]=2(3a+4n-4m)(n-m)2;(4)原式=(x2-x-6)(x2-x-20)=(x-3)(x+2)(x-5)(x+4).