The equation of a circle:
[tex](x-h)^2+(y-k)^2=r^2[/tex]
(h,k) - the coordinates of the centre
r - the radius
[tex]A(2,1) - \hbox{the centre} \\
h=2 \\ k=1 \\ \\
(x-2)^2+(y-1)^2=r^2 \\ \\
\hbox{passes through B(10,7)} \\
x=10 \\
y=7 \\ \\
(10-2)^2+(7-1)^2=r^2 \\
8^2+6^2=r^2 \\
64+36=r^2 \\
r^2=100 \\ \\
\hbox{the equation:} \\ \boxed{(x-2)^2+(y-1)^2=100}[/tex]
