Question 951695
{{{x^2+ y^2-8x+6y+21=0}}} to graph it, first write it in standard form {{{(x-h)^2+(y-k)^2=r^2}}} where {{{h}}} and {{{k}}} are {{{x}}} and {{{y}}} coordinates of the center, and {{{r}}} is a radius

{{{(x^2-8x)+ (y^2+6y)+21=0}}}....complete squares

{{{(x^2-8x+_)-_+ (y^2+6y+_)-_+21=0}}}

{{{(x^2-8x+4^2)-16+ (y^2+6y+3^2)-9+21=0}}}

{{{(x-4)^2+ (y+3)^2-25+21=0}}}

{{{(x-4)^2+ (y+3)^2-4=0}}}

{{{(x-4)^2+ (y+3)^2=4}}}

so,{{{h=4}}} and {{{k=-3}}}, the center is at ({{{4}}},{{{-3}}})
and {{{r=sqrt(4)}}}=>{{{r=2}}}

plot a point ({{{4}}},{{{-3}}}) and draw a circle using {{{r=2}}}

{{{drawing( 600, 600, -5, 10, -10, 5, 
circle(4,-3,.1),locate(4,-3,C(4,-3)),circle(4,-3,2),
graph( 600, 600, -5, 10, -10, 5,0 )) }}}