Réponse:
Exercice 80:
1.
[tex] x = \frac{ - 7}{3} [/tex]
2/
[tex]x = 2[/tex]
3/
[tex]x = - 4[/tex]
4/
[tex]x = 8[/tex]
Exercice 81:
1/ x= -4
2/x=-4
3/x= 12
4/x=-1,2
Explications étape par étape:
Exercice 80 :
1/
[tex]3x + 7 = 0 \\ 3x = - 7 \\ x = \frac{ - 7}{3} [/tex]
2/
[tex]6 - x = 4 \\ - x = 4 - 6 \\ - x = - 2 \\ x = 2[/tex]
3/
[tex]3(x + 7) = 9 \\ 3x + 21 = 9 \\ 3x = 9 - 21 \\ x = \frac{ - 12}{3} \\ x = - 4[/tex]
4/
[tex]x - 8 = 0 \\ x = 8[/tex]
Exercice 81:
1/
3x +7 = x-1
3x-x = -1-7
2x = -8
x = -8÷2
x = -4
2/
6-x = x+14
-x-x = 14-6
-2x = 8
x = 8÷-2
x = -4
3/
3(x+7) = 4x+9
3x+21 = 4x+9
3x-4x = 9-21
-x = -12
x = 12
4/
2(x-4) = 7x-2
2x-8 = 7x-2
2x-7x = -2+8
-5x = 6
x = 6÷-5
x =-1,2
