Question 739122
{{{x^2+y^2+kx+4y-5 =0}}} will pas through the point (5,1).

{{{kx=5-x^2-y^2-4y}}}  if  {{{x=5}}} and {{{y=1}}}

{{{k*5=5-5^2-1^2-4*1}}} 

{{{5k=5-25-1-4}}}
 
{{{5k=-25}}}

{{{k=-5}}}

{{{x^2+y^2-5x+4y-5 =0}}}

{{{(x^2-5x+25/4)-25/4+(y^2+4y+4)-4 =5}}}

{{{(x-5/2)^2+(y+2)^2=5+25/4+4}}}

{{{(x-5/2)^2+(y+2)^2=5+25/4+4}}}

{{{(x-5/2)^2+(y+2)^2=9+25/4}}}

{{{(x-5/2)^2+(y+2)^2=36/4+25/4}}}

{{{(x-5/2)^2+(y+2)^2=61/4}}}

center: ({{{5/2}}},{{{-2}}})

radius: {{{sqrt(61/4)=3.9}}}

{{{drawing( 500, 500, -10, 10, -10, 10,
  
  circle( 2.5, -2, 3.9 ),circle(5,1,0.1),circle(5/2,-2,0.1), grid(1))}}}