00:03
Okay, so we have a function, it's a cost function, marginal cost function, and we're going to figure out the additional cost if we change x from 100 to 150 or from 500 to 550.
00:18
So we're going to do for above.
00:19
So to do that, we're going to use an integral.
00:22
So we're going to write out the integral because i think that's important.
00:25
So we have the integral, we have from 100 to 150, and we have 3 ,000 minus x minus 0 .001.
00:36
X squared, which is equal to, if we integrate this, we get 3 ,000 x minus x squared over 2, minus 0 .001, which in this case, i'm actually going to change 0 .001.
00:52
I'll write it up here.
00:53
I'm going to change 0 .001 to 1 over 3 ,000.
00:58
I think it'll make it a bit easier, with all the numbers and stuff.
01:01
So we're going to do that.
01:03
So here we get, sorry, 1 over 1 ,000.
01:07
There should be 1.
01:09
So we get x squared over 3 ,000.
01:14
X cubed over 3 ,000.
01:16
So we have x cubed over 3 ,000, and we're doing that from 100 to 150.
01:21
If we do that, we get 3 ,000 times 150 minus 150 minus 150 squared divided by 2 minus 150 cubed divided by 3 ,000, minus 350 cubed, divided by 3 ,000, minus 3 ,000.
01:45
Don't forget the parentheses because we're multiple or subtracting times a whole expression times 100 minus 100 squared over 2 minus 100 cubed over 3 ,000.
02:09
If we calculate all those out, we're going to get 450 ,000 minus 11 ,250 ,000, minus 11, 125 ,000, minus 11, 125 ,000, minus 11125, minus 325, minus 325, minus 3 ,000.
02:28
Plus 5 ,000 because remember a negative minus subtracting a negative creates a positive and then we have plus 3 ,333 .33 .3...