Réponse :
a)
7x=28 <=> x =28/7 <=> x = 4
7 +x =28 <=> x = 21
-7x = -28 <=> x = 4
7x = -28 <=> x = -4
7 - x = 28 <=> x = 7-28 <=> x = -21
x-7 = -28 <=> x = -28 +7 <=> x = -21
7+x = -28 <=> x = -28 -7 <=> x = -35
x-7 = 28 <=> x = 28 +7 <=> x= 35
-7x = 28 <=> x = -4
7-x = -28 <=> x = 28 +7 <=> x = 35
2)
-7x = -28 <=> x = 4
7x =28 <=> x = 4
en divisant par -1 l'équation 1, on obtient l’équation 2
je te laisse faire la suite
c)
-x-7 = 28 soit x= -35
-x-7 = -28 soit x= 21
j'espère avoir aidé.
Explications étape par étape
