the radius r of a sphere is increasing at a rate of 3cm/min. find the rate of change of the area when r=3cm

Answer 1

a = 4πr^2
da/dt = 8πr dr/dt

Now just plug in your numbers.

Answer 2

where did 8 come from

Answer 3

hello!?

the derivative of r^2 is 2r

4*2 = 8

?!?!?!??

Answer 4

ohhhh ya sorry I get it