a) first we will calculate the distance between center and given point because this is the radius of circle:
[tex]d=\sqrt{(1-5)^2+(1-0)^2}\\
\\
d=\sqrt{(-4)^2+1}=\sqrt{17}[/tex]
b) Now we will write the equation of the circle:
[tex]\boxed{\boxed{(x-5)^2+y^2=17}}[/tex]