Answer
A = $2x(\sqrt {36-x^2}), 0\leq x \leq 6$
Work Step by Step
Area $A = 2xy = 2x(\sqrt {36-x^2})$ (Use the diagram and the given function to find the area of the rectangle.)
$ 0\leq x \leq 6$ for the expression under the square root to be non-negative.
