a)x+5=8
x = 8-5
x = 3
b)3x-8=6x+2
3x-6x = 2 +8
-3x = 10
x = -10/3
c)2(x-3)=2x-6
2x-6 = 2x-6
d)2x-3=x+7
2x-x = 7+3
x = 10
e)5x+2-x-8=3x-4+7
4x -6 = 3x +3
4x-x = 3+6
3x = 9
x =9/3
x =3
f)(x-4)(x-3)=x*x-7x+12
x²-3x-4x+12 =x²-7x+12
x²-7x+12 =x²-7x+12
g)(x-4)(x-3)=x*x-x+4
x²-3x-4x+12 =x²-x+4
x²-7x+12 =x²-x+4
x²-x²-7x+x = 4 -12
-6x = -8
x = -8/-6
x = 4/3
donc seule les egalites c et f sont vraies