See the image below for a demonstration. Hope this helps out.
First square both sides to get:
c + 22 = (c + 2)^2
or
c + 22 = c^2 + 4c + 4
Move the terms on the left side to the right side:
c^2 + 3c - 18 = 0
Factor to get:
(c + 6) * (c - 3) = 0.
The solutions are c = -6 and c = 3.
Check to see if these answers work by plugging them into the original equation:
c = -6:
sqrt (-6 + 22) ?= -6 + 2
But, -6 + 2 is a negative number, and you can't get a negative from a square root. So, -6 is extraneous.
c = 3:
sqrt (3 + 22) ?= 3 + 2
5 = 5. So, 3 works.
The answer is: B
You should go by 0.001
so you can graph 0.001, 0.002, 0.003, and so on
18.5-0.5= 18
18/3= 6
So r=6
