This looks like the equation of a circle. Let's complete the squares for x and y:
(x^2+6x+9)+(y^2-4y+4)-13-23=0; (x+3)^2+(y-2)^2=36.
The centre of the circle is (-3,2) and the radius is sqrt(36)=6. The standard form is:
((x+3)^2)/6^2+((y-2)^2)/6^2=1.