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2014-03-12T23:36:16+01:00
Exercice 2

a) x = 3
-4(3+3) = 13
-4 x 3 = 13
-12 = 13 Faux

x= 2
-4(2+3) = 13
-4 x 5 = 13
-20 = 13 Faux

b) 4x-7 = -4+3x
x = 3
4x3-7 = -4+3x3
12-7 = -4 +9
5 = 5
Vrai

x= 2
4x2-7 = -4+3x2
8-7 = -4+6
1 = 2
Faux

c) -2(3x+1) = -5x
x=3
-2(3x3+1) = -5x3
-2(9+1) = -15
-2x10 = -15
-20 = -15
Faux

x=2
-2(3x2+1) = -5x2
-2(6+1) = -10
-2x4 = -10
-8 = -10
Faux

Exercie 3
2/6 +5/4 = 2x2/6x2 + 5x3/4x3 = 4/12 + 15/12 = 19/12
1/2 : 13/4 = 1/2 x 4/13 = 4/(2x13) = 2/13
-2/5 x 25/4 = -(2x5x5)/(5x2x2) = 5/2
3/4-2/9x3/2 = 3/4 - (2x3)/(3x3x2) = 3/4-1/2 = 3/4 - 2/4 = 1/4

(2/7) / (3/14) = 2/7x 14/3 = (2x2x7)/(7x3) = 4/3

4-2/12 x 24/2 = 4 - (2x2x12)/(12x2) = 4 - 2 = 2

5/4:5 = 5/4:5/1 = 5/4 x 1/5 = (5x1)/(4x5) = 1/4