因式分解提高题 帮忙

1.
(1-a^2)(1-b^2)-4ab
=1-a^2-b^2+a^2b^2-4ab
=(ab)^2-2ab+1-(a^2+b^2+2ab)
=(ab-1)^2-(a+b)^2
=(ab-1+a+b)(ab-1-a-b)
2.
x^4+x^2+1
=x^4+2x^2+1-x^2
=(x^2+1)^2-x^2
=(x^2+x+1)(x^2-x+1)
3.
2(a^2+b^2)(a+b)^2-(a^2-b^2)^2
=2(a^2+b^2)(a+b)^2-(a+b)^2(a-b)^2
=(a+b)^2(2a^2+2b^2-a^2-b^2-2ab)
=(a+b)^2(a-b)^2
4.
(a-b)^2+4ab-c^2
=(a+b)^2-c^2
=(a+b+c)(a+b-c)
5.
a^4+b
??
6.
a^6-1/64
=a^6-(1/2)^6
=[a^3+(1/2)^3][a^3-(1/2)^3]
=(a+1/2)(a^2-a/2+1/4)(a-1/2)(a^2+a/2+1/4)
7.
x^3-7x-6
=x^3-x-6x-6
=x(x^2-1)-6(x+1)
=x(x+1)(x-1)-6(x+1)
=(x+1)(x^2-x-6)
=(x+1)(x-3)(x+2)

1.拆开，有（b^2-1)a^2-4b*a-(b^2-1)=(ab-a+b+1)(ab+a-b+1)
2.原式=x^4+2x^2+1-x^2=(x^2+x+1)(x^2-x+1)
3.原式=2(a^2+b^2)(a+b)^2-(a+b)^2(a-b)^2=(a+b)^4
4.原式=(a+b)^2-c^2=(a+b+c)(a+b-c)
5..............
6.原式==(a+1/2)(a^2-a/2+1/4)(a-1/2)(a^2+a/2+1/4)
7.原式=x^3-x^2+x^2-