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Most Important Selected Qs for JEE AdvancedMathematicsStraight Lines

Paragraph: Let B ₁ 3 x +4 y -10=0 and B ₂ 4 x -3 y -5=0 are bisectors of angle between lines L ₁=0 and L₂=0 . If L₁ passes through origin and L₂=0 meets the curve y^2=4 a x at A and B . On the basis of above information answer the following : Question: If AB subtends 90^ at origin then a is equal to -

Options

  1. A4 11
  2. B3 11
  3. C5 11
  4. D2 11

Correct answer

C. 5 11

Step-by-step solution

Joint equation of the lines joining A & ~B to origin is aligned & y ^2-4 ax ( 11 x -20 y 20 )=0 & 20 y ^2-44 ax ^2+80 axy =0 aligned As AB subtends 90^ at origin. So 20-44 a =0 a = 5 11

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