The general equation for a circle is:
[tex](x-h)^2+(y-k)^2=r^2[/tex]where (h,k) is the center and r is the radius.
In this case, we have the following:
[tex](x-6)^2+(y+8)^2=81[/tex]Notice that we can write the equation in the following way:
[tex]\begin{gathered} (x-6)^2+(y+8)^2=81 \\ \Rightarrow(x+6)^2+(y-(-8))^2=(9)^2 \end{gathered}[/tex]therefore, the center of the circle is (h,k)=(6,-8) and the radius is r=9
