Réponse :
A = (x - 1)/(x + 1)
1) montrer que A = 1 - 2/x + 1
A = (x - 1)/(x + 1)
= (x - 1 + 2 - 2)/(x + 1)
= (x + 1 - 2)/(x + 1)
= [(x + 1)/(x + 1)] - 2/(x + 1)
= 1 - (2/(x + 1))
2) Montrer que A = [2 x/(x+1)] - 1
A = (x - 1)/(x + 1)
= (x - 1 + x - x + 1 - 1)/(x+1)
= (2 x - x - 1)/(x+1)
= (2 x - ( x + 1))/(x + 1)
= [2 x/(x + 1)] - (x + 1)/(x + 1)
= [2 x/(x + 1)] - 1
Explications étape par étape