An ellipse passes through the foci of the hyperbola, 9 x 2 - 4 y 2 = 36 and its major and minor axes lie…

An ellipse passes through the foci of the hyperbola, 9x2-4y2=36 and its major and minor axes lie along the transverse and conjugate axes of the hyperbola respectively. If the product of eccentricities of the two conics is 12, then which of the following points does not lie on the ellipse?
  1. 392, 3
  2. 132, 32
  3. 132, 6
  4. 13, 0

Solution

Equation of the hyperbola
x24-y29=1



Focus of hyperbola a1e1, 0 and (-a1e1, 0)  

a1=2, e1= 1+94=132

Foci would be +13, 0 and -13, 0 

Product of eccentricity would be 

132 e2=12

  e2= 113 .

As the major & minor axis of the ellipse coincide with axis of hyperbola then the value of a2 for ellipse would be 13 ,

e2=1-b22a22

113=1-b2213

b22=12

Equation of the ellipse would be 

x213+y212=1.

Option (1)  394 (13)+312=1

Satisfies the equation, hence it lies on the ellipse. 

Option (2) 134 (13)+34.12=1

does not lie on the ellipse.

Option (3)  132(13)+612=1 satisfy.

Option (4) 1313+0=1 satisfy.

So, option 132, 32 is the answer.

Asked in: JEE Main 2015 (10 Apr Online)

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