Medium MCQ +4 / -1 PYQ · JEE Mains 2021

If the points of intersections of the ellipse ${{{x^2}} \over {16}} + {{{y^2}} \over {{b^2}}} = 1$ and the
circle x2 + y2 = 4b, b > 4 lie on the curve y2 = 3x2, then b is equal to :

  1. A 12 Correct answer
  2. B 10
  3. C 6
  4. D 5

Solution

${{{x^2}} \over {16}} + {{{y^2}} \over {{b^2}}} = 1$ ... (1)<br><br>${x^2} + {y^2} = 4b$ .... (2)<br><br>${y^2} = 3{x^2}$ .... (3)<br><br>From eq (2) and (3) <br><br>x<sup>2</sup> = b and y<sup>2</sup> = 3b<br><br>From equation (1) <br><br>${b \over {16}} + {{3b} \over {{b^2}}} = 1$<br><br>$\Rightarrow {b^2} + 48 = 16b$<br><br>$\Rightarrow b = 12$

About this question

Subject: Mathematics · Chapter: Conic Sections · Topic: Parabola

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