1.原式=a^2(a^2-12a-28)
=a^2(a-14)(a+3)
2.原式=(x-y-3)(x-y+5)
3.原式=（x^2+2x+3)^2-5(x^2+2x+3)-6
=(x^2+2x+3-6)(x^2+2x+3+1)
=(x-1)(x+3)(x^2+2x+4)
4.原式=x^2+(y-1)x-(2y^2-7y+6)
=x^2+(y-1)x-(2y-3)(y-2)
=(x+2y-3)(x-y+2)
5.根据十字相乘,有k=13,-13,8,-8,7.-7.
6.利用求根法,有原式=
(x-(1/2)-(√(1+4√(√3+1)))/2)(x-(1/2)+(√(1+4√(√3+1)))/2)
LZ若还有什么不懂得话尽管问我.