00:02
Hi here for the given question.
00:03
We are given that we have series we need to check whether they are convergent or divergent.
00:08
We are using p -test series and we are like using comparison test and then using comparison test.
00:15
We are checking the p -series test.
00:17
So here for the first one, we have series summation and running from 1 to infinity and plus 7 divided by n square.
00:23
So this can be further written as summation and running from 1 to infinity 1 plus 7 upon n divided by n.
00:30
So here we have a n equals to 1 plus 7 upon n divided by n, which is less than b n which is equal to 1 upon n.
00:38
So here we know that b n is equal to summation and running from 1 to infinity 1 upon n.
00:44
So here as we can observe that here in our case, this is 1 upon n here.
00:49
We have p equals to 1 which is less than 1 less than or equal to 1.
00:54
So the series will be divergent using p -test.
00:57
So using p -test we have b n as divergent.
01:02
So here by comparison test, we can say that series a n is also divergent.
01:13
So here for the first part the given series is divergent.
01:16
Now here we are given second part.
01:18
We have summation and running from 1 to infinity 2 divided by 2 to the power n plus 5.
01:23
So here now further we know that a n is equal to 2 upon 2 to the power n plus 5.
01:29
This is less than b n which is equal to 1 upon 2 to the power n.
01:33
Now here we know that b n can be further written as 1 by 2 to the power n.
01:38
Now here if we use the value using r -test, then here it is in a geometric series and r is equal to 1 by 2 which is less than 1.
01:48
So here we have b n as a convergent series because if the value of ratio is less than 1, then the series will be convergent.
01:55
So here b n is convergent.
01:58
Therefore by comparison test, we can say that here in our case a n is also convergent...