Bonjour,
A(x) = (x + 2)² - 9
A(x) = x² + 4x + 4 - 9
A(x) = x² + 4x - 5
A(x) = (x + 2)² - 9
A(x) = (x + 2)² - 3²
A(x) = (x + 2 + 3)(x + 2 - 3)
A(x) = (x + 5)(x - 1)
A(3) = 5² - 9 = 25 - 9 = → tu termines
A(√3 - 2) = (√3 - 2 + 2)² - 9 = 3 - 9 → tu termines
A(x) = 0 soit (x + 5)(x - 1) = 0
produit de facteurs nuls :
x + 5 = 0 ou x - 1 = 0
x = -5 ou x = 1
A(x) = -5 soit x² + 4x - 5 = -5
x² + 4x = 0
x(x + 4) = 0
→ tu termines
