00:01
In this problem, we are going to consider an integral of the form from a to b f of x dx.
00:10
And we will also focus on this limit in terms of this riemann sum.
00:18
Summation from i equal to 1 to n, 3i over n squared, 4 plus 3i over n.
00:27
So in the first part, we are going to identify what is delta x, what is xi, a, b and the function itself.
00:38
And in the second part, we are going to actually compute this limit.
00:43
So the idea is that we focus on the most general expression.
00:50
So we have the same limit, summation from i equal to 1 to n, f of xi delta x.
00:57
So delta x is b minus a over n and xi is a plus i times delta x.
01:08
Now let us consider this sum.
01:11
We have 3i over n squared, 4 plus 3i over n.
01:20
So let us notice that we have this ratio 3 over n everywhere.
01:25
So let us try to write everything in terms of that ratio.
01:30
So first i need to make this square by including a factor of 1 over 3 here.
01:37
So we have 1 over 3, 3 over n, 3 over n, i times 4 plus 3 over n times i.
01:49
So now i get this feeling that 3 over n must be the delta x.
01:54
So 1 over 3, delta x times delta x times i times 4 plus i times delta x.
02:04
Okay, then i want to factor out delta x.
02:07
So this will be my factor here and the rest will be the function itself.
02:13
The function evaluated at xi itself i mean.
02:16
So we have 1 over 3, delta x times i times 4 plus delta x times i.
02:27
Okay, now as i have said i got this feeling that delta x must be 3 over n.
02:35
So if that is correct we must have...
02:39
Okay, i am also going to take a equal to 0 to see if i get a consistent picture here.
02:47
Okay, so just using these two we can obtain b equal to 3 and xi equal to 3i over n...