Answer
(a) See graph
(b) $1,000\text{ feet}$
Work Step by Step
(a)
The graph of the equation is as shown.
(b)
One x-intercept for the graph is at $(-500,0)$. Notice from the graph that the symmetry is at $x=0$ which means that half of the width of the arch support is the length from $x=-500$ to $x=0$ which is $500$ units. Then, the width of the arch support which is twice of the length is:
$$500(2)=1,000\text{ feet}$$
