Réponse :
a) 14x + 4 = 13x + 7
14x + 4 - 4 = 13x + 7 - 4
14x = 13x +3
14x - 13x = 13x - 13x +3
x = 3
b) 7x + 15 = 4x + 60
7x + 15 - 15 = 4x + 60 -15
7x = 4x + 45
7x - 4x = 4x - 4x + 45
3x = 45
3x : 3 = 45 : 3
x = 15
c) 5x + 12 = x + 2
5x + 12 - 12 = x +2 -12
5x = x -10
5x - x = x -x -10
4x = -10
4x : 4 = -10 : 4
x = -2.5
d) 6a - 17 = 3a + 22
6a - 17 + 17 = 3a + 22 + 17
6a = 3a + 39
6a -3a = 3a -3a + 39
3a = 39
3a : 3 = 39: 3
a = 13
e)
5y - 23 = 3y + 12
5y - 23 + 23 = 3y +12 + 23
5y = 3y + 35
5y - 3y = 3y - 3y + 35
2y = 35
y = 17.5
f)
11b - 6 = 5b + 30
11b - 6 + 6 = 5b + 30 +6
11b = 5b +36
11b - 5b = 5b-5b+36
6b=36
b = 6
g)
6a - 17 = -4a +23
6a - 17 + 17 = -4a + 23 +17
6a = -4a + 40
6a + 4a = -4a + 4a +40
10a = 40
a = 4
h)
3y -19 = -5y - 3
3y - 19 + 19 = -5y -3+ 19
3y = -5y +16
3y + 5y = -5y + 5y + 16
8y = 16
y = 2
i)
7b - 31 = -5b - 7
7b - 31 + 31 = -5b - 7 + 31
7b = -5b + 24
7b + 5b = -5b + 5b + 24
12b = 24
b = 2
a)
5x+4=-12x+6
5x + 4 - 4 = -12x + 6 - 4
5x = -12x +2
5x + 12x = -12x +12x + 2
17x = 2
x = 2/17
b)
-7y+18=-10y+42
-7y + 18 - 18 = -10y + 42 - 18
-7y = -10y + 24
-7y + 10y = -10y + 10y +24
3y = 24
y = 8
c)
-8y +34= -11y +35
-8y + 34 -34 = - 11y + 35 - 34
-8y = -11y +1
-8y + 11y = -11y + 11y + 1
3y = 1
y = 1/3
d)
-5a +30=-12a +25
-5a +30 -30 = -12a +25-30
-5a = -12a -5
-5a + 12a = -12a + 12a - 5
7a = -5
a = -5/7
e)
9x+27=-2x + 37
9x+27-27=-2x+37-27
9x=-2x+10
9x+2x=10
11x=10
x=10/11
f)
-12b+3=-2b+9
-12b + 3 - 3 = -2b + 9 - 3
-12b = -2b + 6
-12b +2b = -2b +2b + 6
-10b = 6
b = -6/10
Explications étape par étape :
j'ai beaucoup détaillé mes calculs pour que tu comprennes mon raisonnement mais tu n'est pas obligé de copier toutes les étapes de calcul sur ta feuille.
