Bonsoir,
Exercice 7 :
a. -2x + 7 = -x + 9
-2x + 7 + 2x = -x + 9 + 2x
7 = x + 9
7 - 9 = x + 9 - 9
x = -2
b. 4x - 21 = 7x - 9
4x - 21 - 4x = 7x - 9 - 4x
-21 = 3x - 9
-21 + 9 = 3x - 9 + 9
-12 = 3x
3x / 3 = -12 / 3
x = -4
c. -7x - 12 = 8x + 3
-7x - 12 + 7x = 8x + 3 + 7x
-12 = 15x + 3
-12 - 3 = 15x + 3 - 3
-15 = 15x
15x / 15 = -15 / 15
x = -1
d. Tu essaies ? :)
Exercice 8 :
a. 7a - 8 = 3a + 7
7a - 8 - 7a = 3a + 7 - 7a
-8 = -4a + 7
-8 - 7 = -4a + 7 - 7
-15 = -4a
-4a / -4 = -15 / -4
a = 15/4
b. -2a + 3 = 14a - 1
-2a + 3 + 2a = 14a - 1 + 2a
3 = 16a - 1
3 + 1 = 16a - 1 + 1
4 = 16a
16a / 16 = 4 / 16
a = 4/16 = 1/4
c. 3a - 4 = -5a - 8
3a - 4 - 3a = -5a - 8 - 3a
-4 = -8a - 8
-4 + 8 = -8a - 8 + 8
4 = -8a
-8a / -8 = 4 / -8
a = -4/8 = -1/2
d. Tu essaies ? :)
