Question

@sourwing

Answer 1

plz check my answer

Answer 2

differentiate A=pir^2 w.r.t to r.

Answer 3

\[A(r)=\pi r^2\]
A'(r)=?

Answer 4

5pi

Answer 5

25pi

Answer 6

are you trying to find the derivative of r^2 yet?

Answer 7

w.r.t r

Answer 8

\[\frac{dA}{dt}=\pi \frac{d(r^2)}{dr}\]

Answer 9

you can do it
use power rule

Answer 10

d(25)/5d

Answer 11

:(

Answer 12

\[\frac{d(r^2)}{dr}=2r \text{ by power rule }\]

Answer 13

and yes 10 pi ft^2/ft is right