# Thread: Express area as a function of x.

1. ## Express area as a function of x.

Last one today, I swear.

A rectangular plot of land that borders on a river is the be fenced along 3 sides using 400 feet of fencing. Express the area of the fenced in land, A, as a function.

I don't even know how to set this one up. I began solving like this:
A=2x+(400-2x)=400
I know that's not even close. I think I need to terms for the width and the length.

2. Originally Posted by theevilp0ptart
Last one today, I swear.

A rectangular plot of land that borders on a river is the be fenced along 3 sides using 400 feet of fencing. Express the area of the fenced in land, A, as a function.

I don't even know how to set this one up. I began solving like this:
A=2x+(400-2x)=400
I know that's not even close. I think I need to terms for the width and the length.
let the side parallel the river be x. let the other two sides be y

then, x + 2y = 400

and A = xy

take it from here

### 4-x^2=y express the area as a function of x

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