请把(a+3b)(a²-3ab+9b²)-(a-3b)(a²+3ab+9b²)化简

请把(a+3b)(a²-3ab+9b²)-(a-3b)(a²+3ab+9b²)化简
请把(a+3b)(a²-3ab+9b²)-(a-3b)(a²+3ab+9b²)化简

请把(a+3b)(a²-3ab+9b²)-(a-3b)(a²+3ab+9b²)化简
(a+3b)(a²-3ab+9b²)-(a-3b)(a²+3ab+9b²)
=a³-3a²b+9ab²+3a²b-9ab²+27b³-(a³+3a²b+9ab²-3a²b-9ab²-27b³)
=a³-3a²b+9ab²+3a²b-9ab²+27b³-a³-3a²b-9ab²+3a²b+9ab²+27b³
=54b³

a^3+b^3 = (a+b)(a^2-a*b+b^2)
a^3-b^3 = (a-b)(a^2+a*b+b^2)
如果你知道上面两个式子，这道题你就迎刃而解

因为立方和差公式a^3 b^3 = (a b)(a^2-a*b b^2)
a^3-b^3 = (a-b)(a^2 a*b b^2)原式＝a3 9b3－（a3-9b3)=18b3