Question

Is the point P (2,8) on the inside or outside of the circle described with equation x^2+y^2=100?

Answer 1

Points $(x,y)$ on the circle satisfy $x^2+y^2=100$.

Points inside the circle satisfy $x^2+y^2$.

Points outside the circle satisfy $x^2+y^2>100$.

We have

$2^2+8^2=4+64=68$

so the point (2, 8) lies inside the circle.