Réponse :
Bonjour,
Exercice 5.
a. 2x+8 - 12 + 3x = 0
5x - 4 = 0
5x = 4
x = 4/5
b. 2x² + 2x - x - 1 + 3x - 2x² - 12 + 8x = 5
12x -1 -12 - 5 = 0
12x -18=0
12x = 18
x= 18/12 = 6*3 / 6*2 = 3/2
c. (x+1)² - (x-1)² = 0
identité remarquable : a² - b² = (a-b)(a+b)
(x+1-x+1)(x+1+x+1) = 0
2* (2x+2) = 0
4x+8 = 0
4x= -8
x = -8/4 = -2
Exercice 6.
1. E = x² + 2x + 1 + 2x² - 3x + 2x - 3
E = 3x² +x -2
2. E = (x+1)(x+1+2x-3)
E = (x+1)(3x-2)
3. (x+1)(3x-2)=0
deux solutions
soit x+1 = 0
x= -1
soit 3x-2 = 0
3x= 2
x=2/3
Ainsi S = {-1; 2/3}
