# A rectangle has one corner in quadrant 1 on the graph of y=16-x^2, another at the origin, and the third on the positive y-axis, and the fourth on the positive x-axis. How do you express the area, A, of the rectangle as a function of x?

$x \left(16 - {x}^{2}\right)$
for width x in the x direction, the rectangle's height is $y = 16 - {x}^{2}$ so its area is
$x \left(16 - {x}^{2}\right)$