Question

The point $P$ on the parabola $y^2=4ax$ for which $|PR-PQ|$ is maximum, where $R(-a,0),Q(0,a)$ is

• A. $(a,2a)$
• B. $(a,-2a)$
• C. $(4a,4a)$
• D. $(4a,-4a)$

Answer 1

Answer: (A)

$(a,2a)$

We know any side of the triangle is more than the difference of remaining two sides, such that $|PR-PQ|\le RQ$

$\Rightarrow$ The required point $P$ will be the point of intersection of the line $RQ$ with parabola which is $(a,2a)$ as $RQ$ is a tangent to the parabola