Bonsoir
3 x ⁴ + 4 x² - 7 = 0
3 X² + 4 X - 7 = 0
Δ = 16 - 4 ( 3 * - 7 ) = 16 + 84 = 100
x 1 = ( - 4 - 10 ) / 6 = - 14 /6 = - 7 /3
x2 = ( - 4 + 10 ) /6 = 6 /6 = 1
x² = - 7/3 ⇒ pas de solution
x² = 1 ⇒ x = √ 1 ⇒ x = 1
S ( 1 )
( 4 - x² ) ( 3 x² + 8 x - 3 ) > 0
4 - x² > 0 ⇔ x² > 4 ⇒ x > 2 ou > - 2
3 x² + 8 x - 3 > 0
Δ = 64 - 4 ( 3 * - 3 ) = 64 + 36 = 100
x 1 = ( - 8 - 10 ) / 6 = - 18 /6 = - 3
x 2 = ( - 8 + 10 ) / 6 = 2 /6 = 1 /3
