Question 308671
Complete the square in x and y. 
{{{2x^2+2y^2+28x+80=0}}}
{{{(2x^2+28x)+(2y^2)+80=0}}}
{{{(x^2+14x)+(y^2)+40=0}}}
{{{(x^2+14x+49)+(y^2)+40=49}}}
{{{(x+7)^2+(y-0)^2=9}}}
Compare to the general equation of circle with radius R and center (h,k),
{{{(x-h)^2+(y-k)^2=R^2}}}
{{{h=-7}}}
{{{k=0}}}
{{{ R=3 }}}