Bonjour,
A = 2x(x - 4) + (3x - 4)(-2x + 7)
A = (2x² - 8x) + (-6x² + 21x + 8x - 28)
A = 2x² - 8x - 6x² + 29x - 28
A = -4x² + 21x - 28
B = (4 - 5x)(2 - 3x) - (5x + 2)(3 - 4x)
B = (8 - 12x - 10x + 15x²) - (15x - 20x² + 6 - 8x)
B = 8 - 22x + 15x² - 15x + 20x² - 6 + 8x
B = 2 - 29x + 35x²
C = (5x + 4)² + (3 - 2x)(3 + 2x)
C = (25x² + 40x + 16) + (9 - 4x²)
C = 25x² + 40x + 16 + 9 - 4x²
C = 21x² + 40x + 25
