Answer:

Step-by-step explanation:
Given
Required
Determine the area in terms of time
From the question, we have:
-> radius per time
and
--> area from radius
The interpretation of the question is to find the composite function: a(t)
If
, and
, the
Substitute 0.5t for r



B. (k+10f)(k-5f) you can tell in 2 ways. 1. if the second sign is neg then the signs in the factors are going to be one neg and one positive so that knocks out C and D. Then you look at the second term and since the 5 is positive then the 10 has to be positive so you end up with a positive 5kf.
The second way is to FOIL them out. When you check B you get

combine your like terms and you have your original expression of

Hope that helps