00:01
So we have a farmer and he has 950 feet of fencing.
00:09
He wants to enclose a rectangular area and divide it into four pens with fencing parallel to one side.
00:18
So if we want this to become four pens, then i'm going to let this be x and that's y.
00:26
So i have x and x and then i have 1, 2, 3, 4, 5, y.
00:33
So 2x plus 5y is 950.
00:40
Then i want to maximize area.
00:44
So area is x times y.
00:48
So i know that 5y is 950 minus 2x.
00:56
Divide both sides by 5.
01:01
950 divided by 5 is 190 minus 2 over 5x.
01:08
I'm going to take that expression for y, bring it over to my area expression.
01:14
And now i'm going to distribute.
01:19
So i have 190x minus 2 fifths x squared.
01:24
Take the derivative of that using power rule and then i'm going to set that equal to zero.
01:35
I have 4 over 5x equal to 190.
01:40
Multiply both sides by your reciprocal.
01:44
And i'm going to get x equal to 237 .5.
01:55
So first, what do we need? we need an area in terms of x and y.
02:02
So that's this.
02:05
And then we want the given information.
02:10
So that's d.
02:14
And then we want area in one variable.
02:18
So that's this.
02:21
And then we want to solve it.
02:29
So let's keep solving.
02:30
So we have x.
02:32
Now we need y.
02:33
That's 190 minus 2 fifths times 237 .5.
02:40
Which gives me y is 95.
02:50
So the area is 237 .5 times 95...