Answer
$$\eqalign{
& *{\text{ The interval of integration is infinite}}{\text{.}} \cr
& {\text{* The integrand is unbounded on the interval of integration}} \cr} $$
Work Step by Step
$$\eqalign{
& {\text{The improper integral is used for cases in which:}} \cr
& *{\text{ The interval of integration is infinite}}{\text{.}} \cr
& {\text{* The integrand is unbounded on the interval of integration}} \cr} $$
