Bonjour ;
1) (x + 1)(x + 1) = x² + x + x + 1 = x² + 2x + 1 ,
donc : (x + 1)² = (x + 1)(x + 1) = x² + 2x + 1 .
2) (x - 1)(x -1) = x² - x - x + 1 = x² - 2x + 1 ,
donc : (x - 1)² = (x - 1)(x - 1) = x² - 2x + 1 .
3) (x + 4)² = (x +4)(x +4) = x² + 4x + 4x + 16 = x² + 8x + 16 .
(x - 3)² = (x - 3)(x - 3) = x² - 3x - 3x + 9 = x² - 6x + 9 .