a. In the diagram, the inner rectangle in brown shows the pool with length 25 feet and width 10 feet.
The outer rectangle in blue shows a fence with is x feet wide uniformly.
The length of the fence is [tex]25+x+x = 25+2x ft[/tex]
Similarly, the width of the fencing is [tex]10+x+x = 10+2x ft[/tex].
b. Length of fence = [tex]25+2x ft[/tex]
Width of fence = [tex]10+2x ft[/tex]
Area of a rectangle is given as length * width
A = [tex](25+2x)(10+2x)[/tex]
[tex](25+2x)(10+2x) = 250+50x+20x+4x^2[/tex]
A = [tex]4x^2+70x+250[/tex] ft^2
