2) Résoudre dans R : 5x +4=21 3x+3=2 x+8 4x +5=7 x-8 Bonjour pouvez vous m’aider

Réponse:

a) 5x + 4 = 21

= 5x + 4 - 4 = 21 - 4

= 5x = 17

= 5x/ 5 = 17 / 5

= x = 3.4

b) 3x + 3 = 2x + 8

= 3x - 2x = 8 - 3

= 1x = 5

= 1x/1 = 5/ 1

= x = 5

c) 4x + 5 = 7x - 8

= 4x - 7x = -8 -5

= -3x = -12

= -3x/ -3 = -12/ -3

= x = -4