00:01
So this problem asks us to estimate the integral of f by using the rectangle method.
00:09
And if you have the textbook, you can figure out that the function f is a decreasing function.
00:15
That means for upper estimate, you want to use the left end point because the function is decreasing, so the left points will be higher than the right point.
00:32
And similarly, if you want to use the lower estimate, then it will have to be the right end point.
00:44
And once you figure this out, it's just left to write down the end point of each rectangles and the base of each rectangles.
00:55
So for part a, if you want to use five rectangles, then each rectangle will have a base 2.
01:03
And for the upper estimate, it will be the base of each rectangle is 2, multiplied by sum of height.
01:24
In this case, we want to use the left endpoints, so it's from f of 0.
01:29
Remember, each one has base 2, so the next one should be f of 2, and similarly, f of 4, f of 6, f of 8...