In this problem they're asking for is a polynomial expression to describe the area of the surface inside the fence.
The court is 78 x 36 and there is a constant distance (let's call it "x") from the edge of the court to the fence
Therefore, the length of the fence will be 78 + 2x (we're adding x to each side of the court, remember). The width will be 36 + 2x.
To find the area, we must multiply length x width.
[tex]A=(78+2x)\cdot(36+2x)[/tex]Let's simplify this expression
[tex]\begin{gathered} A=78\cdot\: 36+78\cdot\: 2x+2x\cdot\: 36+2x\cdot\: 2x \\ A=2808+228x+4x^2 \end{gathered}[/tex]