bonjour
f (x) = ( x + 2 )² - 9
1. f (x) = x² + 4 x + 4 - 9 = x² + 4 x - 5
2. f (x) = ( x + 2 + 3 ) ( x + 2 - 3 ) = ( x + 5 ) ( x - 1 )
3. f (x) = - 9
( x + 2 )² - 9 = - 9
( x + 2 )² = 0
x = - 2
4. f (x) = 0
( x + 5 ) ( x - 1 ) = 0
x = - 5 ou 1
5. f (x) = - 5
x² + 4 x - 5 = - 5
x² + 4 x = 0
x ( x + 4 ) = 0
x = 0 ou - 4