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

Let \(a>0, b>0\). Let \(e\) and \(\ell\) respectively be the eccentricity and length of the latus rectum of the hyperbola \(\frac{ x ^{2}}{ a ^{2}}-\frac{ y ^{2}}{ b ^{2}}=1\). Let \(e ^{\prime}\) and \(\ell^{\prime}\) respectively the eccentricity and length of the latus rectum of its conjugate hyperbola. If \(e ^{2}=\frac{11}{14} \ell\) and \(\left( e ^{\prime}\right)^{2}=\frac{11}{8} \ell^{\prime}\), then the value of \(77 a+44 b\) is equal to

  1. A \(100\)
  2. B \(110\)
  3. C \(120\)
  4. D \(130\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(130\)

Step-by-step Solution

Detailed explanation

\(e=\sqrt{1+\frac{b^{2}}{a^{2}}}, \ell=\frac{2 b^{2}}{a}\) Given \(e ^{2}=\frac{11}{14} \ell\) \(1+\frac{b^{2}}{a^{2}}=\frac{11}{14} \cdot \frac{2 b^{2}}{a}\) \(\frac{a^{2}+b^{2}}{a^{2}}=\frac{11}{7} \cdot \frac{b^{2}}{a}\)........\((1)\) Also…