Question

If the distance of two points $P$ and $Q$ from the focus of a parabola $y^2=4ax$ are $4$ and $9$ respectively, then the distance of the point of intersection of tangents at $P$ and $Q$ from the focus is

• A. $8$
• B. $6$
• C. $5$
• D. $13$

Answer 1

The correct option is B $6$

If $S$ is focus of the parabola and $T$ is the point of intersection of tangents at $P$ and $Q$, then
${ST}^2=SP\times SQ\Rightarrow {ST}^2=4\times 9\Rightarrow ST=6$