00:01
So this problem asks us to a, find a function that models the cross -sectional area of the gutter in terms of x.
00:09
And b, find the value of x that maximizes the cross -sectional area and see what is the cross -sectional area.
00:15
So the gutter looks like a u shape with sides x, and i'm going to label the bottom part y.
00:22
And since it's a rectangular shape, this side's also x.
00:27
It's the same as the other side.
00:29
And this entire piece is equal to 30 inches.
00:34
So we have 2x plus y is equal to 30.
00:43
And this is staying in the problem.
00:45
So we're trying to find the cross -section area, which is base times height, which is x times y.
00:50
So a is equal to x -y.
00:55
Now, if i solve for y, this top equation, i can sub -y into this equation and get an equation for area that just has xes.
01:05
So i have y is equal to negative 2x plus 30...