What is the equation of a circle with a center at (1,1) and a radius of 5 ?

The equation of a circle:
[tex](x-h)^2+(y-k)^2=r^2[/tex]
where
(h, k) - the coordinates of a center
r - the radius
We have
(1, 1) → h = 1 and k = 1
r = 5
Substitute:
[tex](x-1)^2+(y-1)^2=5^2\\\\(x-1)^2+(y-1)^2=25[/tex]