Question

A=4pi r^{2} solve for r

Answer 1

             A = 4πr²          Divide both sides by 4π
     A / 4π = r²               Find the square root of both sides
√(A / 4π) = √(r²)          Cancel out the square with the square root
√(A / 4π) = r                Switch the sides to make it easier to read
              r = √(A / 4π)