Question 84318
You must complete the square on the x and y terms respectively:
{{{x^2-4x +y^2+2y=-1}}}


You must "complete the square" by taking HALF of the x coefficient, and SQUARE the result, adding this amount to each side of the equation.  Repeat by taking HALF of the Y coefficient, SQUARE, and add to each side of the equation.  It should look like this:

{{{x^2-4x+____+y^2+2y+____=-1+____+____}}}
{{{x^2-4x + 4  +y^2+2y+1=-1+4+1}}}
{{{ (x-2)^2 +(y+1)^2 = 4}}}


The center is at x=2 and y=-1, and r^2 = 4.  
Therefore, the center is (2,-1) and r=2.


R^2 at SCC