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JEE PYQ: Parabola Question 16

Question 16 - 2019 (09 Apr Shift 1)

If one end of a focal chord of the parabola, $y^2 = 16x$ is at $(1, 4)$, then the length of this focal chord is:

(1) $25$

(2) $22$

(3) $24$

(4) $20$

Show Answer

Answer: (1)

Solution

$y^2 = 16x$, $a = 4$. At $(1,4)$: $t = \frac{1}{2}$. Length of focal chord $= a\left(t + \frac{1}{t}\right)^2 = 4\left(\frac{1}{2} + 2\right)^2 = 4 \times \frac{25}{4} = 25$.


Learning Progress: Step 16 of 32 in this series