3)
-infinit ............................-1.....................+1..........................+infinit
_____________________________________________________________
1-x +++++++++++++++++++++++++++++++0- - - - - - - - - - - - - - - - - -
_____________________________________________________________
x+1 - - - - - - - - - - - - - - - - - - 0 +++++++++++++++++++++++++++++++
_____________________________________________________________
(1-x)/(1+x) - - - - - - - - - - - - - - - -l++++++++++++0----------------------------------
Deci (1-x)/(x+1) este negativa pt. x=(-infinit, -1)U(+1, +infinit), pozitiva
pt. x=(-1,+1) si este zero pt. x=1