拆项分解因式分解 1、a的4次方-11倍a的平方+1.2、X的3次方+X+2 3、X的3次方—7X—6

我不知道对不对,
1.a4-11a2+1=a4-11a2+30-29-a=(a2-5)(a2-6)-29
2.x3+x+2=x3-x+2x+x
=x(x2-1)+2x+2
=x(x+1)(x-1)+2(x+1)
=(x+1)[x(x-1)+2]
3.x3-7x-6
=x3-x-6x-6
=x(x2-1)-6(x+1)
=x(x+1)(x-1)-6(x+1)
=(x+1)[x(x-1)-6]