Réponse:
Exercice 5 :
-5/4 + x/2 = -2 + 3/4x
-5/4 + 2x/4 = -8/4 + 3/4x
2x/4 + 3/4x = -8/4 + 5/4
5/4x = -3/4
5/4x × 4 = -3/4 × 4
5x = -3
5x × 1/5 = -3 × 1/5
x = -3/5
Exercice 6 :
Premièrement :
1/5 ÷ (3/4 -5/6)
= 1/5 ÷ (9/12 -10/12)
= 1/5 ÷ -1/12
= 1/5 × -12/1
= -12/5
Deuxièment :
(4/5 -8) ÷ 3
= (4/5 -40/5) ÷ 3
= -36/5 ÷ 3
= -36/5 × 1/3
= -12/5
Donc : -12/5 = -12/5
Alors : cette égalité est vraie .
Exercice 7 :
F= 7xy -14xy
F= 7× (xy - 2xy)
G= 2a (b-3) -b ( b-3)
G= (b-3) (2a -b) .
