alis00 (9а^2-6ав+в^2)-(9а^2+6ав+в^2)=9а^2-6ав+в^2- 9а^2-6ав-в^2= 12ав

limbo696 (3а-в)^2-(3а+в)^2 = 9a^2-6ab-b^2-9a^2-6ab-b^2=-12ab