(1)::\int \frac{\left ( \frac{25}{9} \right )^{x}}{\left ( \frac{15}{9} \right )^{x}-1} dx
\int \frac{\left ( \frac{5}{3} \right )^{2x}}{\left ( \frac{5}{3} \right )^{x}-1} dx
let\, \, \left ( \frac{5}{3} \right )^{x} =t \Rightarrow \left ( \frac{5}{3} \right )^{x} log\left ( \frac{5}{3} \right )dx =dt
integral\, \, is \, \, \frac{ 1}{log\left ( \frac{5}{3} \right )}\int \frac{t^{2}}{(t-1)t}dt
\frac{1}{log\left ( \frac{5}{3} \right )}\int \frac{tdt}{t-1}
which can be easily done