$\"\"$

Integral test: \ \

The function $\"\"$ is a continuous, positive, decreasing function on $\"\"$ and let $\"\"$ . \ \

(i) If $\"\"$ is convergent, then $\"\"$ is convergent. \ \

(ii) If $\"\"$ is divergent, then $\"\"$ is divergent.

$\"\"$

The series is $\"\"$ .

The function $\"\"$ is oscuillated in between $\"\"$ and $\"\"$ . \ \

So the function is not positive and non decreasing in the interval.

Therefore, the integral test can not be used to find the series $\"\"$ is convergent.

$\"\"$

The function $\"\"$ is neither positive nor decreasing. \ \