Graph a Circle in General Form x^2 + y^2 -10x + 2y +21 = 0 - Algebra IA 08-0202

Graphing circles in standard form is just a matter of identifying the center and the radius. The difficulty comes when the circle is not given in standard form. In this case, when given general form, we will complete the square twice as illustrated below.
step 1: Group all terms with variable x and group all terms with variable y.
step 2: Complete the square for each grouping.
step 3: Be sure to add (b/2)^2 to both sides of the equation.
step 4: After factoring, identify the center and radius.

[Wildboyelias]

where did the -1 in the center come from

[ronaldoEscalanteCruz]

what if your stuck and cant complete the square to get the center.