Explications étape par étape :
a. 2x + 9 = 0
⇔ 2x = -9
⇔ x = -9/2
b. 5 - 4x = 0
⇔ -4x = -5
⇔ 4x = 5
⇔ x = 5/4
c. 6r - 7 = 0
⇔ 6r = 7
⇔ r = 7/6
d. 8-3x = 0
⇔ -3x = -8
⇔ 3x = 8
⇔ x = 8/3
e. 6x + 42 = 0
⇔ 6x = -42
⇔ x = -7
f. 5 - 2.5 = 0 pas de solution
g. Pas de solution
h - 8x = 0
⇔ x = 0
