$\"\"$

The series is $\"\"$ .

The series is in the form of geometric series.

Here the first term $\"\"$ and common ratio is $\"\"$ .

If the series is cinverges, then $\"\"$ .

$\"\"$

$\"\"$ .

Therefore, the interval of convergence is $\"\"$ .

$\"\"$

The sum of the series in geometric series is $\"\"$ .

$\"\"$ .

The sum of the series is $\"\"$ .

$\"\"$

Interval of convergence is $\"\"$ .

The sum of the series is $\"\"$ .