Bonjour
1)
f (x) = (x + 3)² - 25
f (x) = x² + 6x + 9 - 25
f (x) = x² + 6x - 16
2)
f (x) = (x + 3)² - 25
f (x) = (x + 3)² - (5)²
f (x) = (x + 3 - 5) (x + 3 + 5)
f (x) = (x - 2) (x + 8)
3)
a)
f (x) = 0
(x- 2) (x + 8) = 0
x - 2 = 0 ou x + 8 = 0
x = 2 x = - 8
b)
f (x) = - 16
x² + 6x - 16 = - 16
x² + 6x - 16 + 16 = 0
x² + 6x = 0
x (x + 6) = 0
x = 0 ou x + 6 = 0
x = - 6
c)
f (x) = 11
x² + 6x - 16 = 11
x² + 6x - 16 - 11 = 0
x² + 6x - 27 = 0
(x - 3) (x + 9) = 0
x - 3 = 0 ou x + 9 = 0
x = 3 x = - 9.
