check the picture below.
since the circle is tangent to the y-axis, namely just touching it, it's radius is, well, you can see it right there in the picture.
[tex]\bf \textit{equation of a circle}\\\\
(x- h)^2+(y- k)^2= r^2
\qquad
center~~(\stackrel{-3}{ h},\stackrel{2}{ k})\qquad \qquad
radius=\stackrel{3}{ r}
\\\\\\\
[x-(-3)]^2+[y-2]^2=3^2\implies (x+3)^2+(y-2)^2=9[/tex]
