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Question: If the eccentricity of the ellipse \(\frac{x^{2}}{a^{2} + 2} + \frac{y^{2}}{a^{2} + 5}\)= 1 be\(\fra...

If the eccentricity of the ellipse x2a2+2+y2a2+5\frac{x^{2}}{a^{2} + 2} + \frac{y^{2}}{a^{2} + 5}= 1 be13\frac{1}{\sqrt{3}}, then length of latus rectum of ellipse is

A

4

B

186\frac{18}{\sqrt{6}}

C

106\frac{10}{\sqrt{6}}

D

8

Answer

4

Explanation

Solution

Clearly a2 + 5 > a2 + 2

So (a2 + 2) = (a2 + 5) (113)\left( 1 - \frac{1}{3} \right)

3a2 + 6 = 2a2 + 10 Ž a2 = 4

\ equation of ellipse is x26+y29=1\frac{x^{2}}{6} + \frac{y^{2}}{9} = 1

\ length of latus rectum = 2×63=4\frac{2 \times 6}{3} = 4