can anyone help with circles?

x^2 + 4x       + y^2 + 6y   = 51     complete the square for x and y

(x+2)^2         + (y+3)^2     = 51 + 4 + 9          this is a circle with center  -2 -3   and radius 8  

 

 

x^2 + 4         +   y^2 + 6y    = 3

(x+2)^2         + (y+3)^2      = 3   + 4 + 9            this is a circle with center  -2 -3  and radius  4      (diameter 8)

You can factor and use the circle formula, which is:

\((x – h)^2 + (y – k)^2 = r^2\)

the center (h, k) and the radius r