Question

Solve it:-
Does the point $\left(-2.5,3.5\right)$ lie inside ,outside or inside the circle $x^2+y^2=25?$

Answer 1

$(x_1,y_1)=(-2.5,3.5)$

$S=x^2+y^2-25$

$S_{11}=(-2.5{)}^2+(3.5{)}^2-25$

$S_{11}=-6.5\Rightarrow S_{11}<0$

As $S_{11}<0$ the point lies inside the circle