Explications étape par étape :
EX1
5x - 1 = 4x + 6
⇔ x = 7 réponse B
4x - 1 = 2 - x 2x + 1 = x - 3
⇔ 5x = 3 ⇔ x = -4
⇔ x = 3/5
Réponse B
x² + x - 2 = 0
Δ = 1 - 4 * [( 1* (-2 )] = 9
x₁ = ( -1 - 3) / 2 = -2
x₂ = ( - 1 + 3 ) / 2 = 1
Réponse C
Ex2
a 8x - 4 = 3x + 1
⇔ 5x = 5
⇔ x = 1
b 5 - 4t = -2 + 5t
⇔ 9t = 7
⇔ t = 7/9
c 1 + 2/3y = 3/2
⇔ 2/3y = 1/2
⇔ y = 3/4
d -0,8 - 1,9k = 2 ( 1 - k )
⇔ -0,8 - 1,9k = 2 - 2k
⇔ 0,1k = 2,8
⇔ k = 28
