Răspuns:
(x+2)²= x² +2x+4
(x-1)² = x²-2x+1
(3x+2)²= 9x²+12x+4
(2x-1)²= 4x²- 4x+1
(2x-1)(2x+1) = 4x²-1
(1/2 a - b)(1/2 a +b))= 1/4a²-b²
