Question

If the point (1, 5) lies on a circle whose center is at the origin, what is the equation of the circle?


x2 + y2 = 26
x2 + y2 = 16
x2 + y2 = 13
x2 + y2 = 11

Answer 1

the equation of a circle is
x^2 + y^2 = r^2

where r is the length of the radius
I would find the distance between the center at (0,0) and (1,5) (a point on the circle)
that distance will be r
if you square it, it will give you r^2, so you will know which choice is correct.