Voici quelques modifications:

(x - 1) (2x + 3) - (x - 1) (2-x) = (x-1) (3x + 1).
(2x + 1)² + (2x + 1) (x + 3) = (2x + 1) (3x + 4).
(5x - 2) (2x + 7) - (5x - 2) = (5x - 2) (-2x - 7) .
7x - 49 + 14x² = 7 (x - 7 + 2x²).
9x² + 12x + 4 = (3x + 2)².
(2x + 7) (x + 4) - (2x - 7) (4x + 1) = (2x - 7) - (3x - 3).
(4x - 1)² + (2x - 5) (4x - 1) = (4x - 1) (6x - 6).
(x + 7) (3x - 1) + 7x + 49 = (x + 7) (3x + 6).
9x² + 30x + 25 = (3x + 5)².
25x² - 1 - (4x - 3) (5x + 1) = (5x + 1) (x + 2).
4x² - 4x + 1 = (2x - 1)².
x² + x + 0,25 = (x + 0,5)².
100x² - 1 000x + 2 500 = x² - 10x + 25 = (10x + 50)².
(3x - 1)² - (x + 2)² = (2x - 3) (4x + 1).

Sauf erreur de ma part.