bonjour
P (x) = 0.4 x² + 0.8 x - 1.2
Δ = 0.8 ² - 4 ( 0.4 * - 1.2 ) = 0.64 + 1.92 = 2.56 = 1.6 ²
x 1 = ( - 0.8 - 1.6 ) / 0.8 = - 2.4 / - 0.8 = 3
x 2 = ( - 0.8 + 1.6) / 0.8 = 0.8/0.8 = 1
donc correct
p (x) = 3.5 x² - 14 x + 7
Δ = ( - 14 )² - 4 ( 3.5 x 7 ) = 196 - 98 = 98 = ( 7 √2)²
x 1 = ( 14 - 7 √2 ) / 7 = 2 - √2
x 2 = ( 14 + 7 √2 ) / 7 = 2 + √2
donc incorrect
f (x) = - 1.4 x² + 6.16 x - 6.776
Δ = 6.16² - 4 ( - 1.4 x - 6.776 ) = 37.9456 - 37. 9456
Δ = 0
x 0 = - 6.16 / - 2.8 = 2.2
correct
f (x) = 2 x² - 14 x
2 x ( x - 7 ) = 0
x = 0 ou 7
correct
