bonjour
x² - 12 x - 28
Δ = ( -12) ² - 4 ( 1 * - 28 )
Δ = 144 + 112 = 256 = 16 ²
x ₁ = ( 12 + 16 ) / 2 = 28/2 = 14
x ₂ = ( 12 - 16 ) / 2 = - 4 /2 = - 2
x² + 6 x + 14
Δ = 6² - 4 ( 1 * 14 ) = 36 - 56 = - 20
Δ < 0 donc pas de solution
x² + 10 x + 21 = 0
Δ = 10² - 4 ( 1 * 21 ) = 100 - 84 = 16 = 4²
x ₁ = ( - 10 + 4 ) / 2 = - 8 /2 = - 4
x ₂ = ( - 10 - 4 ) /2 = - 14/2 = - 7
- 3 x² - 6 x + 24 = 0
Δ = ( - 6 )² - 4 ( - 3 * 24) = 36 + 288 = 324 = 18²
x ₁ = ( 6 + 18 ) / - 6 = - 24 /6 = - 4
x ₂ = ( 6 - 18 ) / - 6 = - 12 / - 6 = 2
