(a-3)² - (a+2)² = ?
(a-3)² = (a-3).(a-3) = a²-3a-3a+9= a²-6a+9 (a+2)²= (a+2).(a+2) = a²+2a+2a+4= a²+4a+4 (a-3)²-(a+2)²= (a²-6a+9) -(a²+4a+4)= a²-a² -6a-4a+9-4= 0-10a+5= -10a+5