Question

A circle has the equation (x−13)2+(y−1)2=4.

Answer 1

An equation of circle has form

$(x-x_0)^2+(y-y_0)^2=r^2 \\ where\: x_0\: and\: y_0\: are\: the\: center$

So, the center is (13;1)

Now we need to find a radius

Let's create an equation

${r}^{2} = 4 \\ r = \sqrt{4} \\ r = 2$

So radius is 2