Sagot :
Bonjour,
4x² - 6x + 7 = 15
⇔ 4x² - 6x - 8 = 0
⇔ 2x² - 3x - 4 = 0
Δ = (-3)² - 4x2x(-4) = 9 + 32 = 41
⇒ 2 solutions : x = (3 - √41)/4 (≈ -0,85) et x = (3 + √41)/4 ≈ 2,35
bonjour
4 x² - 6 x + 7 = 15
4 x² - 6 x + 7 - 15 = 0
4 x² - 6 x - 8 = 0
Δ = ( - 6 )² - 4 ( 4 * - 8 ) = 36 + 128 = 164 = ( 2 √41)²
x 1 = ( 6 - 2 √41 ) / 8 = 3 - √41 / 4
x 2 = ( 6 + 2 √41) / 8 = 3 + √41 /4