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JEE Main202228 Jun 2022Evening ShiftMathematicsParabolaActual

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

Options

  1. A2
  2. B8
  3. C12
  4. D16

Correct answer

B. 8

Step-by-step solution

Plotting the graph with given data we have, We know that, in any parabola, the length of the latus rectum = 4 a and perpendicular distance from vertex to the directrix = a So, a = 8 + 3 - 21 4 2 + - 3 2 ⇒ a = - 10 5 = 2 Therefore, the length of the latus rectum 4 a = 4 × 2 = 8

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