Réponses

2014-01-09T08:14:34+01:00
1) x²-5x = 0
x(x-5) = 0
2 s0lutions
x = 0
et x-5 = 0 x = 5

2) (x-3)²-(x-3)(2x+1) = 0
(x-3)(x-3-(2x+1)) = 0
(x-3) (x-3-2x-1)
(x-3)(-x-4) = 0
2 solutions
x-3 = 0 x = 3
-x-4 = 0 x = -4

3) (3x-7)-(x+1) = 0
3x-7-x-1 = 0
2x-8 = 0
2x = 8
x = 8/2
x = 4

4) (x-3)(x+1)(2-3x) = 0
3 solutions
x-3 = 0 x=3
x+1 = 0 x=-1
2-3x = 0 -3x = -2 x = 2/3

5) x²+5 = 0
x²= -5  impossible un carré est toujours > 0

x²-7 = 0
x² = 7
2 solutions x=V7 et x=-V7 (V se lit racine de)