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If b and c are the lengths of the segments of any focal chord of a parabola y^2=4 a x , then the length of the semi-latus rectum is :

Options

  1. Ab c b+c
  2. Bb c
  3. Cb+c 2
  4. D2 b c b+c

Correct answer

D. 2 b c b+c

Step-by-step solution

Since the semi latus rectum of a parabola is the harmonic mean between the segments of any focal chord of the parabola. l is the harmonic mean between b and c . Hence, l= 2 b c b+c

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