解1、(3x^2y-2x+1）(-2xy)=-6x^3y^2+4x^2y-2xy
2、(2x-1)(x-3)=2x^2-6x-x+3=2x^2-7x+3
3、(-4x-y)(4x-y)=(-y)^2-(4x)^2=y^2-16x^2
4、-3a(a-b)^2=-3a(a^2-2ab+b^2)=-3a^3+6a^2b-3ab^2
5、(a+2b-3c)(a-2b-3c)=[(a-3c）+2b][(a-3c)-2b]=(a-3c)^2-(2b)^2=a^2-6ac+9c^2-4b^2
6、(2a+b)^2(2a-b)^2=[(2a+b)(2a-b)]^2=(4a^2-b^2)^2=16a^4-8a^2b^2+b^4