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QJEEM24Mae9f9: JEE Main 2024 Mathematics - Class 11 JEEM24Mae9f9 Solution: Let the foci of a hyperbola coincide with the foci of the…

Let the foci of a hyperbola HH coincide with the foci of the ellipse E:(x−1)2100+(y−1)275=1E: \frac{(x-1)^2}{100}+\frac{(y-1)^2}{75}=1 and the eccentricity of the hyperbola HH be the reciprocal of the eccentricity of the ellipse EE . If the length of the transverse axis of HH is α\alpha and the length of its conjugate axis is β\beta , then 3α2+2β23 \alpha^2+2 \beta^2 is equal to

Multiple Choice Options

  • A 225
  • B 237
  • C 242
  • D 205

Step-by-Step Verified Solution

E:(x−1)2100+(y−1)275=1E: \frac{(x-1)^2}{100}+\frac{(y-1)^2}{75}=1

 Eccentricity of ellipse, eEamp;=1−b2a2amp;=1−75100amp;eE=12\begin{aligned}\text { Eccentricity of ellipse, } e_E & =\sqrt{1-\frac{b^2}{a^2}} \\& =\sqrt{1-\frac{75}{100}} \\& e_E=\frac{1}{2}\end{aligned}

∴eH=2\therefore e_H=2 [ as eccentricity of hyperbola is reciprocal of eccentricity of ellipse]

Transverse axis of hyperbola =α=\alpha

Conjugate axis of hyperbola =β=\beta

Also, foci of ellipse (1±ae,1)(1 \pm a e, 1)

amp;=(1±(10×12),1)amp;=(1±5,1)amp;=(6,1) and (−4,1)\begin{aligned}& =\left(1 \pm\left(10 \times \frac{1}{2}\right), 1\right) \\& =(1 \pm 5,1) \\& =(6,1) \text { and }(-4,1)\end{aligned}

Distance between foci =10=10

amp;2ae=10amp;⇒a=52\begin{aligned}& 2 a e=10 \\& \Rightarrow a=\frac{5}{2}\end{aligned}

amp; also, e2=1+b2a2amp;4amp;=1+4b225b2amp;=754bamp;=752amp;⇒α=5amp; and β=75amp;3α2+2β2=3(5)2+2(75)=225\begin{aligned}& \text { also, } e^2=1+\frac{b^2}{a^2} \\& \begin{aligned}4 & =1+\frac{4 b^2}{25} \\b^2 & =\frac{75}{4} \\b & =\frac{\sqrt{75}}{2}\end{aligned} \\& \Rightarrow \quad \alpha=5 \\& \text { and } \beta=\sqrt{75} \\& 3 \alpha^2+2 \beta^2=3(5)^2+2(75)=225\end{aligned}

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