00:01
This question says we have a rectangular enclosure where one side is a river.
00:04
We have 320 feet of fencing available and we want to make the maximum area.
00:11
So if we give dimensions to this, so let's say this is x and this is y, our fencing, the 320, is going to equal those three pieces.
00:22
So x and x, so that's 2x and then plus y will make up the 320.
00:30
Now area is going to be x times y.
00:34
I want to maximize area but first i have to get rid of one of these variables.
00:39
So if i come over here and i bring the 2x to the other side, so minus 2x and then equals y, now i can fill this in for y in this equation.
00:50
So i'm going to say a equals x times 320 minus 2x.
00:58
That's a equals 320x minus 2x squared.
01:05
Now this is a quadratic.
01:08
It's an upside down parabola because the a is negative...