bonjour
exercice 1
8 x + 6 = 5 x + 3
8 x - 5 x = 3 - 6
3 x = - 3
x = - 1
4 ( 2 x - 1 ) + 8 = 4 ( 3 x - 1 )
8 x - 4 + 8 = 12 x - 4
8 x - 12 x = - 4 + 4 - 8
- 4 x = - 8
x = 2
4 x + y = - 10
- 5 x + 3 y = 21
y = - 10 - 4 x
- 5 x + 3 ( - 10 - 4 x ) = 21
- 5 x - 30 - 12 x = 21
- 17 x = 21 + 30
- 17 x = 51
x = - 51/17 = - 3
4 x + y = - 10
4*-3 + y = - 10
y = - 10 + 12
y = 2
S ( - 3 ; 2 )
soit x les moins de 18 ans et y les adultes
x + y = 45
15 x + 25 y = 955
x = 45 - y
15 ( 45 - y) + 25 y = 955
675 - 15 y + 25 y = 955
10 y = 955 - 675
10 y = 280
y = 28
x + y = 45
x + 28 = 45
x = 45 - 28
x = 17
17 personnes de - de 18 ans et 28 adultes
