Sagot :
bonsoir
f (x) = - 3 ( x + 2 )² + 27
f (x) = - 3 ( x² + 4 x + 4 ) + 27
f (x) = - 3 x² - 12 x - 12 + 27 = - 3 x² - 12 x + 15
f(x)= - 3 ( x - 1 ) ( x + 5 )
f (x) = -3 ( x² + 5 x - x - 5 )
f (x) = - 3 x² - 15 x + 3 x + 15 = - 3 x² - 12 x + 15
- 3 ( x - 1 ) ( x + 5 ) = 0
x = 1 ou - 5
f ( - 2 ) = - 3 ( - 2 )² - 12 * -2 + 15 = - 12 + 24 + 15 = 27
- 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
f (x ) = 15
- 3 x² - 12 x + 15 - 15 = 0
- 3 x ( x - 4 ) = 0
x = 0 ou 4