A rectangle is inscribed with its base on the x {\displaystyle x} -axis and its upper corners on the parabola y = 4 − x 2 {\displaystyle y=4-x^{2}} , as shown. What is the height of such a rectangle with the greatest possible area?
-axis and its upper corners on the parabola 
, as shown. What is the height of such a rectangle with the greatest possible area?
