00:01
In this question, we are asked to find the formula for the given sum.
00:04
First, we'll expand the square inside the sum.
00:08
Using the square of a sum formula, we'll get 16 plus 2 times 4 times 3 times k over n plus 9 times k squared over n squared, k from 1 to n.
00:28
We'll get the sum 16 plus 24k over n plus 9k squared over n squared.
00:37
Then we'll rewrite this as separate sums.
00:48
As 16 times the sum of ones, n times, plus 24 over n multiplied by the sum of k.
00:59
We factor out n because the expression inside, the index of summation doesn't depend on n, right? so, and n doesn't depend on the index of summation k.
01:08
So, we can factor it out.
01:11
Plus 9 over n squared multiplied by the sum of k squared.
01:20
Now, we'll use the formulas.
01:22
Recall that the sum of ones is simply n.
01:26
The sum of k from 1 to, i apologize, it should be n here, not infinity...