Bonjour,
a. (13 - 7x)(4x + 9) = 0
cela revient à résoudre les équations suivantes :
⇒ 13 - 7x = 0
-7x = 0 - 13
-7x = -13
x = -13/-7 = 13/7
⇒ 4x + 9 = 0
4x = 0 - 9
4x = -9
x = -9/4
b. 4x(-3x - 7) = 0
⇒ 4x = 0
x = 0
⇒ -3x - 7 =0
-3x = 0 + 7
-3x = 7
x = -7/3
c. 7(2x - 5)(3x + 6) = 0
⇒ 2x - 5 = 0
2x = 0 + 5
2x = 5
x = 5/2
⇒ 3x + 6 = 0
3x = 0 - 6
3x = -6
x = -6/3 = -2
d. Tu essaies ? :)
Exercice 2 :
(5x - 2)(2 - 3x) + (4x + 3)(5x - 2) = 0
sous forme factorisée :
(5x - 2)(2 - 3x) + (4x + 3)(5x - 2) = 0
(5x - 2)[(2 - 3x) + (4x + 3)]
(5x - 2)(2 - 3x + 4x + 3)
(5x - 2)(x + 5)
résolution :
(5x - 2)(x + 5) = 0
⇒ 5x - 2 = 0
5x = 0 + 2
5x = 2
x = 2/5
⇒ x + 5 = 0
x = 0 - 5
x = -5