Question

Which of the following points lies on the circle whose center is at the origin and whose radius is 10?

Answer 1

Since the standard form of the circle is:

(x-h)^2+(y-k)^2=r^2, and (h,k)=(0,0) and r=10 so we have:

x^2+y^2=100   Looking at the points you have:

(√10, 0) does not work as (√10)^2+0^2=10+0=10

(0, 2√5) does not work as 0^2+(2√5)^2=0+20=20

(5√2, 5√2) works as (5√2)^2+(5√2)^2=50+50=100