10-2. Parabola, Ellipse, Hyperbola
hard

यदि दीर्घवृत्त  $\frac{{{x^2}}}{{16}} + \frac{{{y^2}}}{{{b^2}}} = 1$ की नाभियाँ व  अतिपरवलय $\frac{{{x^2}}}{{144}} - \frac{{{y^2}}}{{81}} = \frac{1}{{25}}$ की नाभियाँ सम्पाती हों तो ${b^2}$ का मान है  

A

$1$

B

$5$

C

$7$

D

$9$

(AIEEE-2003)

Solution

(c) अतिपरवलय $\frac{{{x^2}}}{{144}} – \frac{{{y^2}}}{{81}} = \frac{1}{{25}}$

$a = \sqrt {\frac{{144}}{{25}}} ,\,\,b = \sqrt {\frac{{81}}{{25}}} ,\,\,{e_1} = \sqrt {1 + \frac{{81}}{{144}}} $

$= \sqrt {\frac{{225}}{{144}}}  = \frac{{15}}{{12}} = \frac{5}{4}$

अत: नाभि $ = (a{e_1},0) = \left( {\frac{{12}}{5}.\frac{5}{4},0} \right) = (3,\,0)$

अत: दीर्घवृत्त की नाभि अर्थात् $ = (4e,0)$ $ \equiv $$(3,\,0)$

 ${x^2} $ अत: ${b^2} = 16\left( {1 – \frac{9}{{16}}} \right) = 7$

Standard 11
Mathematics

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