Bonjour,
1) x = -7
donc : E = (-7 + 3)² - 5(-7 + 3) = 36
2) E = (x + 3)² - 5(x + 3)
= x² + 6x + 9 - 5x - 15
= x² + x - 24
3) E = (x + 3)² - 5(x + 3)
= (x+3)(x+3) - 5(x+3)
= (x+3)(x+3-5)
= (x+3)(x-2)
4) E = 0
⇒ (x+3)(x-2) = 0
⇒ x+3=0 ou x-2=0
⇒ x=-3 ou x=2
