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  • If vertex of a parabola is and the equation of its directrix is <img alt="\mathrm{4 x-3 y=21}" src="https://e

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

Option: 1

2


Option: 2

8


Option: 3

12


Option: 4

16


Answers (1)

best_answer

\mathrm{a=} distance between vertex and directrix

   \mathrm{=\frac{|4(2)-3(-1)-21|}{\sqrt{4^{2}+3^{2}}}} \\

   \mathrm{=\frac{10}{5}} \\

   \mathrm{=2}

\text { Length of L . R.} =4 a=8

Hence the correct option is 2

Posted by

Anam Khan

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