Bonjour,
A = 7x² + (x+3)(1 - x)
A = 7x² + x * 1 + x * (-x) + 3 * 1 + 3 * (-x)
A = 7x² + x - x² + 3 - 3x
A = 6x² - 2x + 3
B = 3(x + 5) + (-x + 2)(x + 5)
B = 3 * x + 3 * 5 - x * x - x * 5 + 2 * x + 2 * 5
B = 3x + 15 - x² - 5x + 2x + 10
B = -x² + 25
C = 9x² - (x + 4)(2x + 2)
C = 9x² - x * 2x - x * 2 - 4 * 2x - 4 * 2
C = 9x² - 2x² - 2x - 8x - 8
C = 7x² − 10x − 8
