resoudre les equation suivantes : a) 7x + 2 = 6x +1 b) 2(x + 3) = 6x - 15 c) 9 = x(2x + 3) - 2x puissance 2

a)
7x + 2 = 6x +1
7x - 6x = 1 - 2
x  = - 1



b)
2(x + 3) = 6x - 15
2x + 6 = 6x - 15
2x - 6x = - 15 - 6
- 4x = - 21
 4x = 21
 x = 21/4



c)
9 = x(2x + 3) - 2x²
9 = 2x² + 3x - 2x²
9 =  3x
9/3 =  x
x = 3

7x+2 =6x+1
7x-6x = 1-2
x = -1

2(x+3) = 6x -15
2x+6 -6x = -15
-4x = -15-6
-4x = -21
x = -21/-4
x = 21/4

9 = x(2x+3) -2x²
9 = 2x²+3x-2x²
9 = 3x
x = 9/3
x = 3