bonjour
3 (x - 5 ) ( x + 8 ) = ( 3 x - 15 ) ( x + 8 )
= 3 x² + 24 x - 15 x - 120
= 3 x² + 9 x - 120
α = - 9 / 6
β = 3 ( - 9/6)² +9 ( - 9 /6 ) - 120
β = 3 * 81/36 - 81/6 - 120
β = 243 /36 - 486/36 - 4 320/36 = 4 563 /36 = 507 / 4
3 ( x + 3/2 )² - 507 /4 est la forme canonique
