1) The first step is to divide the coefficient b by 2
[tex]\begin{gathered} b=6\therefore\frac{6}{2}=3 \\ b=-\frac{4}{2}\therefore=-\frac{4}{2}=-2 \end{gathered}[/tex]2) So now, let's add to both sides those squared numbers to both sides of the equation and then write them as binomials:
[tex]\begin{gathered} x^2+6x+3^2+y^2-4x+(-2)^2=-9+9+4 \\ (x+3)^2+(y-2)^2=4 \end{gathered}[/tex]Note that this is the Equation of the Circle in its standard form, whose radius is 4