Bonjour,
a. (5x + 7)(x - 3) - (x - 3)(x + 2)
= (x - 3)[(5x + 7) - (x + 2)]
= (x + 3)(5x + 7 - x - 2)
= (x +3)(4x + 5)
b. A vous.
c. (x - 3)² + x - 3
= (x - 3)² + (x - 3)
= (x - 3)(x - 3)
= (x - 3)²
d. (x + 3)(x - 3) - 5(x - 3)
= (x - 3)[(x + 3) - 5]
= (x - 3)(x + 3 - 5)
= (x - 3)(x - 2)