Réponses

2013-05-14T20:32:06+02:00
* veut dire multiplié
/ veut dire divisé

A) 3/2x-5=x+7
1,5x= x+7+5
1,5x= x+12
1,5x-x = 12
0,5x = 12
x = 12/0,5
x = 24

B) 2x-1/4 = x/3+6
2x= x/3+6+1/4
2x -x/3 = 6+1/4
x(2-1/3) = 24/4 +1/4
5/3x =25/4
x =( 25/4)/(5/3)
x = 25/4* 3/5
x = 75/20
x = 3,75

C) x/3 + 1/2 = x/2 + 1/3
x/3 -x/2 = 1/3 -1/2
2x/6 - 3x/6 = 2/6 - 3/6
-1x/6 = -1/6
x = (-1/6)/(-1/6)
x = 1

D) ???

E) (3x-5)/5 = (3x+8)/6
3x/5 -5/5 = 3x/6 + 8/6
3x/5 -1 = 3x/(2*3) + 8/6
3x/5 -1 = x/2 + 8/6
3x/5 - x/2 = 8/6 +1
6x/10 - 5x/10 = 8/6 + 6/6
1x/10 = 14/6
1/10*x = 7/3
x = (7/3)/(1/10)
x = 7/3 * 10/1
x = 7/3 * 10
x = 70/3

F) 2/3x + 1/4 = 1/5 - 1/2x
2/3x + 1/2x = 1/5 - 1/4
4/6x + 3/6x = 4/20 - 5/20
7/6x = -1/20
x = (-1/20)/(7/6)
x = -1/20*6/7
x = -6/140
x = -3/70