Question

Упростите выражение
a³+27b³-(a+3b)(a²-3b+9b²)

Answer 1

$a^3+27b^3-(a+3b)(a^2-3b+9b^2)=\\\\= a^3+27b^3- (a^3-3ab+9ab^2+3a^2b-9b^2+27b^3)=\\\\= a^3+27b^3- a^3+3ab-9ab^2-3a^2b+9b^2-27b^3 =\\\\= 3ab-9ab^2-3a^2b+9b^2$