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JEE Mains · Maths · STD 11 - 10.2 parabola,ellipse,hyperbola

यदि दीर्घवृत्त \(4 x ^{2}+ y ^{2}=8\) के बिन्दुओं \((1,2)\) तथा \(( a , b )\) पर खींची गई स्पर्श रेखाएँ परस्पर लम्बवत् है, तो \(a ^{2}\) बराबर है 

  1. A \(\frac{2}{{17}}\)
  2. B \(\frac{4}{{17}}\)
  3. C \(\frac{64}{{17}}\)
  4. D \(\frac{128}{{17}}\)
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Answer & Solution

Correct Answer

(A) \(\frac{2}{{17}}\)

Step-by-step Solution

Detailed explanation

\(4{a^2} + {b^2} = 8\,\,\,\,\,\,.......\left( 1 \right)\) \({\left( {\frac{{dy}}{{dx}}} \right)_{\left( {1,2} \right)}} = - \frac{{4x}}{y} = - 2\) \( \Rightarrow - \frac{{4a}}{b} = \frac{1}{2}\) \(b = - 8a\) \( \Rightarrow {b^2} = 64{a^2}\) \(68{a^2} = 8,{a^2} = \frac{2}{{17}}\)
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