The general equation of a circle is written like [tex](x-h)^2+(y-k)^2=r^2[/tex], where (h,k) is the centre and r is the radius.
Firstly, we're given that the centre is (8,6).
Plug this into the general equation:
[tex](x-h)^2+(y-k)^2=r^2\\(x-8)^2+(y-6)^2=r^2[/tex]
We're given this other point on the circumference of the circle, (8,0), which is 6 units away from the center.
Therefore, the radius is 6 units. Plug this into the general equation too:
[tex](x-8)^2+(y-6)^2=r^2\\(x-8)^2+(y-6)^2=6^2\\(x-8)^2+(y-6)^2=36[/tex]
[tex](x-8)^2+(y-6)^2=36[/tex]