Answer
$a_{5}=a_{1}\times r^{4}=\dfrac {4}{5}\times \left( \dfrac {5}{2}\right) ^{4}=\dfrac {125}{4};$
$a_{n}=a_{1}\times r^{n-1}=\dfrac {4}{5}\times \left( \dfrac {2}{5}\right) ^{n-1}$
Work Step by Step
$r=\dfrac {\dfrac {25}{2}}{5}=\dfrac {5}{2}=\dfrac {2}{\dfrac {4}{5}}=\dfrac {5}{2};a_{1}=\dfrac {4}{5}\Rightarrow a_{5}=a_{1}\times r^{4}=\dfrac {4}{5}\times \left( \dfrac {5}{2}\right) ^{4}=\dfrac {125}{4};a_{n}=a_{1}\times r^{n-1}=\dfrac {4}{5}\times \left( \dfrac {2}{5}\right) ^{n-1}$
