Réponse :
bonjour
f (x) = ( 3 x + 5)² - ( 6 x - 1 )²
f (x) = 9 x² + 30 x +25 - ( 36 x² - 12 x + 1 )
f (x) = 9 x² + 30 x + 25 - 36 x² + 12 x - 1
f (x) = - 27 x² + 42 x + 24
f (x) = ( 3 x + 5 + 6 x - 1 ) ( 3 x + 5 - 6 x + 1 )
f (x) = ( 9 x + 4 ) ( - 3 x + 6 )
f (x) = - 3 ( 9 x + 4 ) ( x - 2)
f (x) = 0
9 x + 4 = 0 ⇔ x = - 4/9
x - 2 = 0 ⇔ x = 2
