Question

Calc question...

Answer 1

aight

Answer 2

Would you fill in the blanks?
A =
dA/dt =

Answer 3

I'm not entirely sure if this is the correct way or not, so please pardon me if I approached the problem incorrectly. I reasoned that if dr/dt=2, then dr=2dt so integrating we have\[\int\limits dr=\int\limits 2dt\] which gives \[r=2t\]Substituting 2t for r in the area formula we get
\[A=π(2t)^2=4πt^2\] So differentiating A with respect to t would yield\[dA/dt=8πt \]Substituting r/2 for t would give us\[8π(r/2)\]And when r=4, dA/dt will equal 16π.