$15a^3+10a^2b-9a-6b$

A cura di: Francesco Speciale

Svolgimento:
$15a^3+10a^2b-9a-6b=5a^2(3a+2b)-3(3a+2b)=$
$=(5a^2-3)(3a+2b)=(sqrt5a+sqrt3)(sqrt5a-sqrt3)(3a+2b)$.