Show that the function $f: R ightarrow R$ defined by $$ f(x)=\left\{\begin{array}{ccc} x & \text { if } & x \leq 1 W x+1 & \text { if } & x>1 \end{array} ight. $$ is not continuous if $R$ is the set of real numbers with the usual topology. CS.VS. 1440