$\"\"$

Theorem 9.9 :

$\"\"$ Term test for divergence: $\"\"$ then $\"\"$ diverges.

$\"\"$

The series is $\"\"$ .

If $\"\"$ convergence, then $\"\"$ .

Find $\"\"$ .

$\"\"$

As $\"\"$ , $\"\"$ .

$\"\"$

$\"\"$ .

Therefore, the sequence is divergent.

$\"\"$

$\"\"$ .

$\"\"$ is divergent.