（1）6a^3-9a^2b^2c （2）-2m^3+8m^2-12m (3)2分之1a^2b^3-2a^2b+3ab^2 (4)3a(x+y)-2b(x+y)

1,原式=3a^2(2a-3b^2C)2.原式=-2m(m^2-4m+3)=-2m(m-3)(m-1)3.原式=1/2ab(ab^2-4a+6b)4.原式=（x+y)(3a-2b)5.原式=3x(x-y)(x-2)6.原式=5a(a-b)[(a-b)^2+3a]=5a(a-b)(a^2-2ab+b^2+3a)