A veterinarian is enclosing a rectangular outdoor running area against his building for the dogs he cares for (see image). He wants to maximize the area using 108 feet of fencing.

ANSWER
The width that will give the maximum area is 27 feet. The maximum area is 1458 square feet.
EXPLANATION
The equation that gives the area is a quadratic function,
[tex]A(x)=x(108-2x)[/tex]To find the width that maximizes the area, we have to find the x-coordinate of the vertex of this parabola. We can observe in the equation that the leading coefficient is -2, so the vertex is the maximum.
First, apply the distributive property to write the equation in standard form,
[tex]A(x)=-2x^2+108x[/tex]The x-coordinate of the vertex of a parabola if the equation is in standard form is,
[tex]\begin{gathered} y=ax^2+bx+c \\ \\ x_{vertex}=\frac{-b}{2a} \end{gathered}[/tex]In this case, b = 108 and a = -2,
[tex]x_{vertex}=\frac{-108}{-2\cdot2}=\frac{108}{4}=27[/tex]Hence, the width that will give the maximum area is 27 feet.
To find the maximum area, we have to find A(27),
[tex]A(27)=27(108-2\cdot27)=27(108-54)=27\cdot54=1458[/tex]Hence, the maximum area is 1458 square feet.