bonjour
f (x) = 3 x² - 12 x - 15
3 x² - 12 x - 15 = 0
Δ = 144 - 4 ( 3 * -15 ) = 144 + 180 = 324
x 1 = ( 12 - 18 ) / 6 = - 6 /6 = - 1
x 2 = ( 12 + 18 ) / 6 = 30/6 = 5
tu as donc les antécédents
3 x² - 12 x - 15 = - 27
3 x² - 12 x - 15 + 27 = 0
3 x² - 12 x + 12 = 0
Δ = 144 - 4 ( 3 * 12) = 144 - 144 = 0
Δ = 0 donc une seule solution
= 12/6 = 2
