Given the center [tex](x_0,y_0)[/tex] and the radius [tex]r[/tex] of a circle, its equation is
[tex](x-x_0)^2+(y-y_0)^2=r^2[/tex]
In your case, the center is (-4,0), and the radius is 2. Plug these values into the generic formula and you'll get the equation.
