bonjour
a) tu mets sous dénominateur commun x + 6
donc x - 1 - 3 x - 18 = 0
- 2 x = 18 + 1
- 2 x = 19
x = - 19/2
b) 4 - x = 7 x - 7
- x - 7 x = - 7 - 4
- 8 x = - 11
x = 11/8
c) 5 - 5 x = 8 - 20 x
- 5 x + 20 x = 8 - 5
15 x = 3
x = 3/15 = 1/5
d) x + 2 x - x² + 6 - 3 x = 0
- x² = - 6
x = √6