Explications étape par étape:
on va d´abord factoriser.
a) = ( 5x+ 1)(1 - 7x - 3x - 7) = 0
(5x + 1)(-10x -6) =0
soit 5x + 1 = 0. 5x = -1 x = -1/5= -0,2
soit -10x -6 = 0. -10x = 6 x = 6/-10 = -0,6
b) = (4x + 7)² = 0
4x + 7 = 0 4x = -7 x = -7/4= -1,75
c) = (2x + 1 + 5x + 13)(2x + 1 - 5x - 13) = 0
(7x + 14)(-3x -12) = 0
soit 7x + 14 = 0 7x = -14. x = -14/7 = -2
soit -3x - 12 = 0 -3x = 12 x = 12/-3 = -4
