Bonjour,
d) 3x + 2 = x - 10
3x - x = -10 - 2
2x = -12
x = -12/2 = -6
e) (5x - 2) + (6x + 9) = 0
5x - 2 + 6x + 9 = 0
11x + 7 = 0
11x = 0 - 7
11x = -7
x = -7/11
i) 3 - 7x = -4(3x + 2)
3 - 7x = -12x - 8
-7x + 12x = -8 - 3
5x = -11
x = -11/5
j) 4x² - 25 = 0
(2x - 5)(2x + 5) = 0
⇒ 2x - 5 = 0
2x = 0 + 5
2x = 5
x = 5/2 = 2,5
⇒ 2x + 5 = 0
2x = 0 - 5
2x = -5
x = -5 / 2 = -2,5
k) (x- 3)² - 4 = 0
(x - 3 - 2)(x - 3 + 2) = 0
(x - 5)(x - 1) = 0
⇒ x - 5 = 0
x = 5 + 0
x = 5
⇒ x - 1 = 0
x = 0 + 1
x = 1
