中二數學問題求幫忙(15點)

Simplify
1.(5a^3-a)+(6a^2-7a+1)-(2a^3+4a-1)
=5a^3-a+6a^2-7a+1-2a^3-4a+1
=3a^3+6a^2-12a+2
2.(3a+1)(a-2)
=3a^2-6a+a-2
=3a^2-5a-2
3.(2x^2-3x+1)(x^2-x-1)
=2x^4-2x^3-2x^2-3x^3+3x^2+3x+x^2-x-1
=2x^4-5x^3+2x^2-2x-1
Factorize
1.3a^2b-6ab^2
=3ab(a-2b)
2.-3xy^2z+6x^2yz^2-9xy^2z^2
=-3xyz(-y-2xz+3yz)
=3xyz(2xz+y-3yz)
3.x^2-6x+9
=(x-3)^2
4.x^2-36
=(x+6)(x-6)