Let's use the variable x to represent the width of the pool.
Since the length is 4 feet longer than the width, the length is "x + 4"
If we add 1 foot for each side of the pool, we will add 2 feet in the length and 2 feet in the width. So the new width is "x + 2" and the new length is "x + 6".
Then, the area of the pool is the product of length and width, so we have:
[tex]\begin{gathered} \text{Area}=(x+6)(x+2) \\ \text{Area}=x^2+8x+12 \end{gathered}[/tex]