If vertex of a parabola is $(2,-1)$ and the equation of its directrix is $4 x-3 y=21$, then the length of…

If vertex of a parabola is $(2,-1)$ and the equation of its directrix is $4 x-3 y=21$, then the length of its latus rectum is

  1. 2

  2. 8

  3. 12

  4. 16

Solution




We are given that directrix of the parabola is $4 x-3 y=21$ and vertex of the parabola is $(2,-1)$
Now $a=\frac{|8+3-21|}{5}=\frac{10}{5}=2$
$\therefore \quad$ latus rectum of the parabola $=4 a=8$

Asked in: BITSAT 2023 (Memory Based Paper 2)

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