bonjour
je fais le 4
1) 3 x - 4 ( x - 5) = 0
3 x - 4 x + 20 = 0
- x = - 20
x = 20
2) 3 x - ( x - 5) = 0
3 x - x + 5 = 0
2 x = - 5
x = - 5/2
3) ( 3 x - 4) ( x - 5) = 0
x = 4/3 ou 5
4) ( x - 1) ( x - 2) - x²
= x² - 2 x - x + 2 - x²
= - 3 x + 2
5) 7 x² - 21 x = 7 x ( x - 3 )
6) - 2 x - 14 ≤ - 16
- 2 x ≤ - 16 + 14
- 2 x ≤ - 2
x ≥ 1
7) second = x
premier = x + 70
troisième = x - 80
x + x+ 70 + x - 80 = 320
3 x = 320 - 70 + 80
3 x =330
x = 110
second = 110 , premier = 180 et troisième = 30
