The formula for the circumference c of a circle with radius r is c = 2πr. which of the following is a formula for π (pi) of the circle in terms of the circumference and radius?
a. pi=c+2r
b. c-2r
c. pi=2r/c
d. pi/c/2r

The formula for the circumference C of a circle with radius r is

Now you should express in terms of C and r. Divide the previous equation by 2r:

correct choice is D.

the solution is h=10 because you add 9 to each side of the equation.

none of the above.

for one of the equations to be used in the process, there has to be a term in the equation since squared is .

since there is only a term in the first equation, we cannot derive a from completing the square.

solving with completing the square