(7+x)+x=15
I did trial and error to get x=4.
Answer:
<h2> 21 km </h2>
Step-by-step explanation:
If the bicyclist travels 7 km for every 5 minutes then it is directly proportional
5 min 7 km
15 min x

Given that
, we have
, so that

Take the derivative and find the critical points of
:

Take the second derivative and evaluate it at the critical point:

Since
is positive for all
, the critical point is a minimum.
At the critical point, we get the minimum value
.
The formula for the area of a circle is

so you simply plug your value for radius into the equation!

Square 14

And Multiply by pi!
615.75 cm^2 approximately!
I hope this helps!