Question

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


Q(1, 11)


R(2, 4)


S(4, -4)


T(9, -2)

Answer 1

The general equation for a circle centered at (h,k) with radius, R, is
(x-h)^2+(y-k)^2=R^2
In this case,
(x-6)2+(y-1)^2=5^2
(x-6)^2+(y-1)^2=25
Now test each point with this formula and see which ones make the formula correct.

Example: (1,11)
(1-6)^2+(11-1)^2=25
(-5)^2+(10)^2=25
25+100=25
125=25
False, so point Q is not on the circle.
Do the same for the remaining points.