$\"\"$ \ \

The function is $\"\"$ . \ \

The power series is $\"\"$ .

The above series is a geometric series with common ratio $\"\"$ .

Geometric series is convergent when common ratio $\"\"$ .

Therefore, the series is convergent if $\"\"$

$\"\"$

Interval of convergence is $\"\"$ .

$\"\"$

$\"\"$ and

Interval of convergence is $\"\"$ .