Question

What is the equations of a circle at (4,5) and a radius of 2

Answer 1

Equation of any circle with (a,b) as its center, and on (x,y) coordinate, with radius r, is:
$(x-a)^2+(y-b)^2=r^2$
so here the center is at (4,5) with radius of 2, so,
The equation of this circle is:
$(x-4)^2+(y-5)^2=4$

Hope this helps.