Réponses

  • Utilisateur Brainly
2014-04-03T06:18:54+02:00
A) 2(x+1)+5=7
2x+2+5=7
2x=0
x=0

b) 2(x+1)+5=6+x
2x+2+5=x+6
2x-x=-1
x=-1

c) 2(x+1)+5=3x²-x+1
2x+2+5=3x²-x+1
3x²-3x-6=0
x²-x-2=0
(x+1)(x-2)=0
x+1=0 ou x-2=0
x=-1 ou x=2

d) 2(x+1)+5=(x+3)(4-x)
2x+7=-x²+4x-3x+12
x²+2x-4x+3x+7-12=0
x²+x-5=0
x=(-1-√21)/2 ou x=(-1+√21)/2