$$\eqalign{
& y = {{3x + 1} \over {1 - x}}\,\,\left( {D = R\backslash \left\{ 1 \right\}} \right) \cr
& y = {{3x + 1} \over { - x + 1}} \cr
& y' = {{3 + 1} \over {{{\left( { - x + 1} \right)}^2}}} = {4 \over {{{\left( { - x + 1} \right)}^2}}} > 0\,\,\forall x \in D \cr
& \Rightarrow Ham\,\,so\,\,DB/\left( { - \infty ;1} \right);\left( {1; + \infty } \right) \cr} $$
