Question

Which point lies on a circle with a radius of 5 units and center at P(6, 1)?

A.
Q(1, 11)

B.
R(2, 4)

C.
S(4, -4)

D.
T(9, -2)

Answer 1

One method would be simply to graph the circle as described and visually inspect to see which of the points is on the circle.

Alternatively, an algebraic method would be to write the equation for the circle and plug in each point to see which one makes the equation equal on both sides.

General equation for a circle: (x-h)^2 + (y-k)^2 = r^2 where (h,k) is the center and r is the radius. Plug in the center and radius of the circle. From there, you can go through the choices one by one and plug in the x and y values of the point. Proceed until you can find a point that satisfies the equation.