Question

Which describes the locus of points 4 units from (5, 1) in the coordinate plane?

Answer 1

center: (5,1) ---> h = 5, k = 1
radius: 4 ----> r = 4


(x-h)^2+(y-k)^2=r^2

(x-5)^2+(y-1)^2=4^2

(x-5)^2+(y-1)^2=16


and that's all there is to it