When dividing fractions, it is most to change a mixed number into a

Into an improper fraction. An improper fraction is a fraction where the denominator is smaller than the numerator. 

Example: Mixed number: 1 2/3
                Improper fraction: 5/3 

X^2 - 4x +(4/2^2) + y^2 + 8y + (8/2^2) = -4 + (4/2^2) + (8/2^2)(x + 2)^2 + (y + 4)^2 = -4 + 4 + 16your center is (-2, -4) and the radius is the sqrt of -4 + 4 + 16 which is 4