Explications étape par étape:
3x + 4 = 2x + 9
<=> 3x - 2x = 9 - 4
<=> x = 5
2x + 3 = 3x - 5
<=> 3 + 5 = 3x - 2x
<=> 8 = x
5x - 1 = 2x + 4
<=> 5x - 2x = 4 + 1
<=> 3x = 5
<=> x = 5/3
3x + 1 = 7x + 5
<=> 1 - 5 = 7x - 3x
<=> - 4 = 4x
<=> x = - 4/4
<=> x = - 1
4x + 3 - ( x + 1) + 5 = 5x + 7
<=> 4x + 3 - x - 1 + 5 = 5x + 7
<=> 3x + 7 = 5x + 7
<=> 7 - 7 = 5x - 3x
<=> 0 = 2x
<=> x = 0
2x + 1 - (2 + x) - 7 = 3x + 7
<=> 2x + 1 - 2 - x - 7 = 3x + 7
<=> x - 8 = 3x + 7
<=> - 8 - 7 = 3x - x
<=> - 15 = 2x
<=> x = - 15/2 ou x = - 7.5
5(x - 1) + 3(2 - x) = 0
<=> 5x - 5 + 6 - 3x = 0
<=> 2x + 1 = 0
<=> 2x = -1
<=> x = - 1/2
7(x + 4) - 3(x + 2) = x + 7
<=> 7x + 28 - 3x - 6 = x + 7
<=> 4x + 22 = x + 7
<=> 4x - x = 7 - 22
<=> 3x = - 15
<=> x = - 5
2(x - 1) - 3(x + 1) = 4(x -2)
<=> 2x - 2 - 3x - 3 = 4x - 8
<=> - x - 5 = 4x - 8
<=> - 5 + 8 = 4x + x
<=> 3 = 5x
<=> x = 3/5
5(3x - 1) - (1 - 2x) = 3(5x - 2)
<=> 15x - 5 - 1 + 2x = 15x - 6
<=> 17x - 6 = 15x - 6
<=> 17x - 15x = - 6 + 6
<=> 2x = 0
<=> x = 0
(x + 2)(x + 1) = (x + 4)(x - 5)
<=> x² + x + 2x + 2 = x² - 5x + 4x - 20
<=> x² + 3x + 2 = x² - x - 20
<=> 3x + x = - 20 - 2
<=> 4x = - 22
<=> x = - 11/2
