bonsoir
f (x) = 2 x² + 4 x - 6
2 x² + 4 x - 6 = 0
Δ = 16 - 4 ( 2 * - 6 ) = 16 + 48 = 64
x 1 = ( - 4 - 8 ) / 4 = - 12 / 4 = - 3
x 2 = ( - 4 + 8 ) / 4 = 4 /4 = 1
donc tu peux déduire ≥ 0
f ( 0) = - 6
f ( - 2 ) = 8 - 8 - 6 = - 6
f ( - 4 ) = 32 - 16 - 6 = 10