Question 308328
Complete the square in x and y. 
{{{3x^2+3y^2+30x+30y+150=0 }}}
{{{(x^2+10x+25)+(y^2+10y+25)+50=25+25}}}
{{{(x+5)^2+(y+5)^2+50=50}}}
{{{(x+5)^2+(y+5)^2=0}}}
The general equation for a circle of radius R centered at (h,k) is,
{{{(x-h)^2+(y-k)^2=R^2}}}
Comparing, it's a circle centered at (-5,-5) with a radius of 0.