Question 321940
Complete the square in x and y.
{{{x^2 + y^2 + 2x -4y + K = 0}}}
{{{x^2+ 2x  + y^2-4y + K = 0}}}
{{{(x^2+ 2x+1)  + (y^2-4y+4) + K = 1+4}}}
{{{(x+1)^2+(y-2)^2=5-K}}}
Compare to the general equation of a circle centered at ({{{h}}},{{{k}}}) with a radius {{{R}}}.
{{{(x-h)^2+(y-k)^2=R^2}}}
{{{R^2=5-K=9}}}
{{{highlight(K=-4)}}}