Question

The equation of a parabola is $y^2=4x$. Let P (1,3) and Q (1,1) are two points in the xy plane. Then,

• A. P and Q are exterior points
• B. P is an interior point while Q is an exterior point
• C. P and Q are interior points
• D. P is an exterior point while Q is an interior point

Answer 1

The correct option is D P is an exterior point while Q is an interior point

Here, $S\equiv y^2-4x=0$
$S(1,3)=3^2-4.1>0$
$\Rightarrow (1,3)isanexteriorpoint.Forthepoint(1,1),S(1,1)=1^1-4.1<0$
$\Rightarrow Q(1,1)$ is an interior point