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

The correct option is A (a, 2a)

We know that any side of the triangle is more than the difference of the remaining two sides so that
$|PR-PQ|\le RQ$
The required point P will be the point of intersection of the line RQ with parabola which is (a, 2a) as PQ is a tangent to the parabola