Bonjour,
Exercice 34
21 -6x -10x -5 = 0
21-5 = 6x+10x
16 = 16x
x= 16/16 = 1
Exercice 39
5/x= 2/7
5 = 2x/7
5*7 = 2x
35 =2x
x= 35/2 = 17,5
Ou
5/2 = 2,5
7* 2,5 = 17,5=x
x/(x+3) = 1/3
x =(1/3)(x+3) =
x = (x+3)/3
3x= x+3
3x-x = 3
2x= 3
x= 3/2 = 1,5
Exercice 86
1)
x
3x
3x+5
2)
3x+5 = 32
3x= 32-5 = 27
x= 27/3 = 9
3)
3x+5 = 2x
3x-2x = -5
x= -5