f (x) = x² + 3 x + 1
f ( 0 = 1
f ( - 4 ) = ( - 4 )² + 3 *-4 + 1 = 16 - 12 + 1 = 5
= courbe pointillé
f (x) = g (x) pour x = - 4 et 0
x² + 3 x + 1 = - x + 1
x² + 3 x + 1 + x - 1 = 0
x² + 4 x = 0
x ( x + 4 = 0
x = 0 ou - 4
