bonsoir
f (x) = x² + 2 x - 3
a) f (x) = ( x + 1 )² - 4
f (x) = x² + 2 x + 1 - 4
f (x) = x² + 2 x- 3
b) f (x) = ( x + 1 - 2 ) ( x + 1 + 2 ) = ( x - 1 ) ( x + 3 )
f (x) = 0
f (x) = ( x- 1 ) ( x + 3 )
x = 1 ou - 3
f (x) = - 3
x² + 2 x - 3 = - 3
x² + 2 x = 0
x ( x + 2 ) = 0
x = 0 ou - 2
