Question 1011104
You want THIS kind of form:  {{{(x-h)^2+(y-k)^2=r^2}}}.


Start with Completing the Squares for the x and y.
{{{x^2+10x+25+y^2-18y+81=49+25+81}}}
{{{(x+5)^2+(y-9)^2=155}}}


radius r=(155)^(1/2)
Center is (-5,9).