计算3a·(-3b)^2·(-2ab)

3a·(-3b)^2·(-2ab)
=3a·9b^2·(-2ab)
=-54a^2·b^3
x^ny·(-x^2y^n)
=-x^(n+2)·y^(n+1)
(2a+b)^2-(2a+b)(2a-b)
=4a^2+4ab+b^2-(4a^2-b^2)
=4a^2+4ab+b^2-4a^2+b^2
=4ab+2b^2
(3a^2)^3-6a^3(2a^3+3a^2+a)
=27a^6-12a^6-18a^5-6^4
=15a^6-18a^5-6a^4
(2a+3b)^2(3b-2a)^2
=(2a+3b)^2(2a-3b)^2
=(4a^2-9b^2)^2
=16a^4-72a^2·b^2+81b^4
(x-2y+3)(x+2y-3)
=x^2-(2y-3)^2
=x^2-(4y^2-12y+9)
=x^2-4y^2+12y-9