Bonsoir,
a) (x + 6)(5 + x)
= x * 5 + x * x + 6 * 5 + 6 * x
= 5x + x² + 30 + 6x
= x² + 6x + 5x + 30
= x² + 11x + 30
b) (4x - 5)(x + 3)
= 4x * x + 4x * 3 - 5 * x - 5 * 3
= 4x² + 12x - 5x - 15
= 4x² + 7x - 15
c) (4 + x)(x - 5)
= 4 * x - 5 * 4 + x * x - 5 * x
= 4x - 20 + x² - 5x
= x² + 4x - 5x - 20
= x² - x - 20
d) (2x - 7)(2x - 1)
= 2x * 2x - 1 * 2x - 7 * 2x - 7 * (-1)
= 4x² - 2x - 14x + 7
= 4x² - 16x + 7
