$\,(x\,-\,a)^2\,+\,(y\,-\,b)^2\,=\,r^2\;\Rightarrow [x\,-\,(-1)]^2\,+\,[y\,-\,(-3)]^2\,=\,4^2\;\Rightarrow \;$
$\,\Rightarrow (x\,+\,1)^2\,+\,(y\,+\,3)^2\,=\,16\,$.
Desenvolvendo os quadrados das somas:
$\,x^2\,+\,2x\,+\,1\,+\,y^2\,+\,6y\,+\,9\,=\,16\;\Rightarrow$
$\,\Rightarrow \boxed{\;x^2\,+\,y^2\,+\,2x\,+\,6y\,-\,6\,=\,0\;}\,$
Resposta: $\;\boxed{\;x^2\,+\,y^2\,+\,2x\,+\,6y\,-\,6\,=\,0\;}\,$