rezolvati in R*
(1+x)/x≥2
(1+x)/x-2≥0
(1+x-2x)/x≥0
(1-x)/x≥0
x -∞.......................................0 .........1..............................∞
1-x +++++++++++++++++++++++++0 - - - - - - -
x ----------------------------------0 ++++++++++++++++++++
(1-x)/x - - - - - - -- - -- - | ++++0- - - - - - - -
x∈(0;1]