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2014-02-21T14:49:32+01:00
Exercice 108 :

1. x-2(3x-8) = 0
x-6x+16 = 0
-5x = -16
x = 16/5

2. (x-2)+(3x-8) = 0
x-2+3x-8 = 0
4x-8 = 0
4x = -4
x = -1

3. (x-2)(3x-8) = 0
Soit x-2 = 0
x = 2
Soit 3x-8 = 0
3x = 8
x = 8/3

4. (x-2)(3x-8) = 16
3x²-8x-6x+16 = 16
3x²-14x = 0
x(3x-14) = 0
Soit
x = 0
Soit 3x-14 = 0
3x = 14
x = 14/3

5. (x-2)(3x-8) = -14x
3x²-8x-6x+16 = -14x
3x²-14x+16 = -14x
3x²+16 = 0
3x² = -16
x² = -16/3
x = (-16/3)

Exercice 111 : 

1. 21x²+26x+8 = 21x²
26x+8 = 0
x = 8/26
x = 4/13

2. 3x+2(7x+4) = 0
3x+14x+8 = 0
17x =-8
x = 8/17

3. (3x+2)+(7x+4) = 0
3x+2+7x+4 = 0
10x = -6
x = -6/10
x = -3/5

4. (3x+2)(7x+4) = 0
Soit 3x+2 = 0
3x = -2
x = -2/3
Soit 7x+4 = 0
7x = -4
x = -4/7

5.(3x+2)(7x+4) = 8
21x²+12x+14x+8 = 8
21x²+26x = 0
x(21x+26) = 0
Soit
x = 0
Soit 21x+26 = 0
21x = -26
x = -26/21

6. (3x+2)(7x+4) = 26x
21x²+12x+14x+8 = 26x
21x²+8 = 0
21x² = -8
x² = -8/21
x = √(-8/21)