Question
Question: The locus of the poles of focal chord of the parabola y<sup>2</sup> = 4ax is...
The locus of the poles of focal chord of the parabola y2 = 4ax is
A
x + 2a = 0
B
its directrix
C
x + 4a = 0
D
None
Answer
its directrix
Explanation
Solution
If (h, k) be the pole, then equation of chord
ky = 2a (x + h), it passes through focus (a, 0)
so 2a (a + h) = 0 ̃ a + h = 0 ̃ a + x = 0