00:01
For this problem, we are asked to determine whether the given sequence, e to the power of k over k factorial, is monotonic or not.
00:07
Also, we are asked to determine whether the sequence is bounded or unbounded.
00:11
So to begin, in investigating the monotonicity, we can use the ratio test.
00:20
So, ak divided by ak plus 1, be equal to e to the k over k factorial, times k plus 1 times k factorial, an alternate way of writing k plus 1 factorial, divided by e to the power of k plus 1.
00:36
So we have that the k factorials will divide out, and most of the factors of e will be divided out.
00:44
We'll be left with k plus 1 over e.
00:48
So we can see that the ratio here is actually going to be dependent.
00:53
Particularly we have that if we want to or if we assert we assert k plus 1 over e is greater than 1 then that means that we'd have to have that k plus 1 is greater than e and we know that that would then mean that we have to have k is greater than e minus 1 e is approximately 2 .718, etc., etc.
01:32
So that means that we need to have k is greater than 2, or k must be greater than 1 .718.
01:40
Or so, which since k must be an integer, we actually get that k must be greater than or equal to 2...