Bonjour :)
a) (x + 5)(2x – 8) + (x + 5)(3x – 7) = 0
ab + ac = a(b+c)
(x + 5) (2x – 8 + 3x – 7) = 0
(x + 5) (5x – 15) = 0
soit (x + 5) = 0
x + 5 = 0
x + 5 - 5 = 0 - 5
x = -5
soit (5x – 15) = 0
5x – 15 = 0
5x – 15 + 15 = 0 + 15
5x = 15
5x ÷ 5 = 15 ÷ 3
x = 5
b) (9x – 15)^2 – (9x – 15)(12x - 7) = 0
ab - ac = a(b-c)
(9x – 15)(9x - 15) (9x - 15)(12x - 7)) = 0
(9x – 15) (9x - 15 – (12x - 7)) = 0
(9x – 15) (9x - 15 – 12x + 7) = 0
(9x – 15) (- 3x - 8 ) = 0
soit (9x – 15) = 0
9x – 15 = 0
9x - 15 + 15 = 0 + 15
9x = 15
9x ÷ 9 = 15 ÷ 9
x = 5/3
soit (– 3x - 8) = 0
– 3x -8 = 0
– 3x -8 +8 = 0 + 8
– 3x = 8
-3x ÷ (-3) = 8 ÷ (-3)
x = 8/-3
c) (2x + 3)(x – 4) + (4x – 5)(2x + 3) = 0
comme pour a)
d) (5y - 2)(2y + 1) - 6(5y - 2) = 0
comme pour b)
J'espère t'avoir aidé ;)
