Question 233885
5. pi(r^2+6r+9)-100=pi*r^2 
(please explain this step? I don't understand how the transition took place from moving the "pi" from the front to placing it behind the 100 in the parentheses)? Please write out the step?
-----------------
The left side is the area after r is increased by 3 to (r+3).  Subtracting the 100 makes it equal to the area when the radius was still r.
------------------
6. r^2+6r+9-(100/pi)=r^2 

(this is clear)
7. 6r+9-31.83=0 
(this is clear)
8. 6r=22.83 
(this is clear)
9. r=3.81