Question 1194119
standard equation of a circle is:

{{{(x-h)^2+(y-k)^2=r^2}}} where {{{h}}} and {{{k}}} are coordinates of a center, {{{r}}} is a radius


if center is at ({{{-4}}}, {{{0}}}), means {{{h=-4}}} and {{{k=0}}} 

 and radius {{{r=9}}}

then we have

{{{(x-(-4))^2+(y-0)^2=9^2}}} 

{{{(x+4)^2+y^2=81}}} => your answer


{{{ drawing( 600, 600, -15, 15, -15, 15,
circle(-4,0,.125), locate(-4,0.8,C(-4,0)),
graph( 600, 600, -15, 15, -15, 15, sqrt(81-(x+4)^2), -sqrt(81-(x+4)^2))) }}}