http://i1323.photobucket.com/albums/u599/sodone1/photo5_zpsbd60f746.jpg
as shown in the diagram the region r lies in the first quadrant above the graph of F(x)= 4-x^2 and below the line y=m(x-2). if m is decreasing at the constant rate of -2 units per second how fast is A (m) changing at the instant the line intersects the axis at (0,12)? is the area increasing or decreasing?

Question

http://i1323.photobucket.com/albums/u599/sodone1/photo5_zpsbd60f746.jpg
as shown in the diagram the region r lies in the first quadrant above the graph of F(x)= 4-x^2 and below the line y=m(x-2). if m is decreasing at the constant rate of -2 units per second how fast is A (m) changing at the instant the line intersects the axis at (0,12)? is the area increasing or decreasing?

anonymous · Answer

Hint: find the area $A$, and then find $\dfrac{dA}{dt}$ in terms of $\dfrac{dm}{dt}=-2$, and plug in for the given value.  What part is tripping you up?