if the diameter is 8, then its radius is half that or 4.
[tex]\textit{equation of a circle}\\\\ (x- h)^2+(y- k)^2= r^2 \qquad center~~(\stackrel{-8}{ h},\stackrel{-5}{ k})\qquad \qquad radius=\stackrel{4}{ r} \\\\[-0.35em] ~\dotfill\\\\\ [x-(-8)]^2~~ + ~~[y-(-5)]^2~~ = ~~4^2\implies (x+8)^2+(y+5)^2=16[/tex]
