Bonjour,
Exercice 1
-2a = -8
a = -8/-2 = 4
3x= 7/4
x= (7/4)/3
x = 7/4 * 1/3
x= 7/12
-5x +12 =-3
-5x = -3-12
-5x = -15
x = -15/-5
x= 3
Exercice 2
3a+7 = 3*-1 +7 = -3 +7 = +4
-9+2a = -9 + 2*-1 = -9 -2= -7
4 ≠ -7
donc, non
-3m+3 = -3* -1/2 +3 = 3/2 +3 = 9/6 + 9/6 = 18/6 = 3
2-5m = 2 -5*-1/2 = 2 +5/2 = 4/2 +5/2 = 9/2 = 4,5
3 ≠ 4,5
donc, non
