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NCERT Class XI Mathematics - Conic Sections - Solutions

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Question : 54 of 71
Marks: +1, -0
Vertices (±2, 0), foci (±3, 0)
Solution:  
Vertices are (±2, 0) which lie on x-axis.
So the equation of hyperbola in standard form is x2ay2b2\frac{x^2}{a^{-y^2} b^2} = 1
∴ Vertices are (±2, 0) ⇒ a = 2; Foci are (±3, 0) ⇒ ae = 3
Now, ae = 3 ⇒ e = 3a\frac{3}{a} ⇒ e = 32\frac{3}{2}
We know that b = ae21a\sqrt{e^2-1} ⇒ b = 29412\sqrt{\frac{9}{4}-1} = 2 52\frac{\sqrt{5}}{2} = 5\sqrt{5}
Thus required equation of hyperbola is x2(2)2y2(5)2\frac{x^2}{(2)^2} - \frac{y^2}{(\sqrt{5})^2} = 1 ⇒ x24y25x^2 - \frac{4y^2}{5} = 1
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