a. −2x+7=−x+9
-2x + 7 = x + 9
-2x + x = 9-7
-x = 2+x = -2
Donc la solution est x = -2
b. 4x - 21 = 7x - 9
4x -21 = 7x - 9
4x - 7x = -9 + 21
-3x = 12
x = -4
Donc la solution est x = -4
c. -7x - 12 = 8x + 3
-7x - 12 = 8x + 3
-7x - 9x = 3+ 12
-15 x = 15
x = -1
Donc la solution est x = -1
d. 7x + 13 = -3x - 7
7x + 13 = -3x - 7
7x + 3x = -7 - 13
10x = -20
x = -2
Donc la solution est x = -2