Bonjour,
Je fais le 1)
A (x) = (x + 1)² + 5 (1 - x)
A (x) = x² + 2x + 1 + 5 - 5x
A (x) = x² + 2x - 5x + 1 + 5
A (x) = x² - 3x + 6
B (x) = (2x - 3) (3x + 1) - 2 (x + 4)
B (x) = 6x² + 2x - 9x - 3 - 2x - 8
B (x) = 6x² + 2x - 2x - 9x - 3 - 8
B (x) = 6x² - 9x - 11
C (x) = (2x - 3)² + (3 - 2x) (1 - x)
C (x) = 4x² - 12x + 9 + 3 - 3x - 2x + 2x²
C (x) = 4x² + 2x² - 12x - 3x - 2x + 9 + 3
C (x) = 6x² - 17x + 12.