(1)-2a^3+12a^2-18a
=-2a(a^2-6a+9)
=-2a(a-3)^2
(2)a^2-2ab+b^2-1
=(a-b)^2-1
=(a-b+1)(a-b-1)
(3)x^2-13xy+36y^2
=(x-9y)(x-4y)
(4)3x²+21x+36
=(x+4)(3x+9)
=3(x+4)(x+3)
(5)x^2+7x+12
=(x+4)(x+3)
(6)(x^2-2x)^2-11(x^2-2x)+24
=(x^2-2x-3)(x^2-2x-8)
=(x-3)(x+1)(x-4)(x+2)