Bonjour,
La question 2) t’a déjà été répondu donc je vais faire la 1)
A = (5 - x/2)^2 + (2 - x)(5 - x/2)
1) développer :
A = 25 - 5x + x^2/4 + 10 - x - 5x + x^2/2
A = x^2/4 + (2x^2)/4 - 11x + 35
A = (3x^2)/4 - 11x + 35
2) factoriser :
A = (5 - x/2)(5 - x/2 + 2 - x)
A = (5 - x/2)(7 - x/2 - 2x/2)
A = (5 - x/2)(7 - 3x/2)
3) x = 5 et x = -2
A = (3 * 5^2)/4 - 11 * 5 + 35
A = (3 * 25)/4 - 55 + 35
A = 75/4 - 20
A = 75/4 - 80/4
A = -5/4
A = (5 - (-2)/2)(7 - 3 * (-2)/2)
A = (5 + 1)(7 + 3)
A = 6 * 10
A = 60
