Réponse:
12x × 4 = 20x +28
48x = 20x +28
48x -20x = 28
28x = 28
28x/28 = 28/28
x = 1
(3x-4)(2x+5) = 0
3x-4 = 0
3x = 4
3x/3 = 4/3
x = 4/3
2x+5 = 0
2x = -5
2x/2 = -5/2
x = -5/2
L'équation a deux solutions : 4/3 ou -5/2.
2(3x-4) - (2x+5) = 0
6x -8 -2x -5 = 0
6x -2x = 8+5
4x = 13
4x/4 = 13/4
x = 13/4
(5x-7)² = 0
(5x-7)(5x-7) = 0
5x -7 = 0
5x = 7
5x/5 = 7/5
x = 7/5
5x -7 = 0
5x = 7
5x/5 = 7/5
x = 7/5
donc la solution de cette équation est : 7/5
x² +20x +100 = 0
x² +2×x×10 +10² = 0
(x+10)² = 0
(x+10)(x+10) = 0
x+10 = 0
x = -10
