Bonjour
Développer, puis réduire.
a. (x + 6)(5 + x)
= 5x + x² + 30 + 6x
= x² + 5x + 6x + 30
= x² + 11x + 30
b. (4x - 5)(x + 3)
= 4x² + 12x - 5x - 15
= 4x² + 7x - 15
c. (4 + x)(x - 5)
= 4x - 20 + x² - 5x
= x² + 4x - 5x - 20
= x² - x - 20
d. (2x - 7) (2x - 1)
= 4x² - 2x - 14x + 7
= 4x² - 16x + 7.