Question 969661

{{{x^2+y^2-4x-2y-20=0}}}

{{{(x^2-4x)+(y^2-2y)=20}}}...complete squares

{{{(x^2-4x+b^2)-b^2+(y^2-2y+b^2)-b^2=20}}}

{{{(x^2-4x+2^2)-2^2+(y^2-2y+1^2)-1^2=20}}}

{{{(x-2)^2-4+(y-1)^2-1=20}}}

{{{(x-2)^2+(y-1)^2=20+4+1}}}

{{{(x-2)^2+(y-1)^2=25}}}

so, {{{h=2}}}, {{{k=1}}} and the center is at ({{{2}}}, {{{1}}})

{{{r=5}}}


{{{drawing( 600, 600, -10, 10, -10, 10,
circle(2,1,.12),circle(2,1,5),locate(2,1,C(2,1)),
 graph( 600, 600, -10, 10, -10, 10, 0)) }}}