Question:

Find the equation of the hyperbola satisfying the give conditions: Foci (\(± 3\sqrt5, 0\)), the latus rectum is of length 8.

Updated On: Oct 24, 2023
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Solution and Explanation

Foci (\(± 3\sqrt5, 0\)), the latus rectum is of length 8.
Here, the foci are on the x-axis. 
Therefore, the equation of the hyperbola is of the form \(\frac{x^2}{a^2} – \frac{y^2}{b^2} = 1. \)
Since the foci are (\(± 3\sqrt5, 0\)), \(c = ± 3\sqrt5 . \)
Length of latus rectum = 8
\(⇒\frac{ 2b^2}{a} = 8\)
\(⇒ 2b^2 = 8a\)
\(⇒ b^2 = \frac{8a}{2}\)
\(= 4a\)

We know that 
a2 + b2 = c2
a2 + 4a = 45
a2 + 4a – 45 = 0
a2 + 9a – 5a – 45 = 0
(a + 9) (a -5) = 0
a = -9 or 5

Since a is non-negative, a = 5.

\(∴ b^2 = 4a= 4 \times 5= 20\)
Thus, the equation of the hyperbola is \(\frac{x^2}{25} –\frac{ y^2}{20} = 1\)

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Concepts Used:

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Hyperbola is the locus of all the points in a plane such that the difference in their distances from two fixed points in the plane is constant.

Hyperbola is made up of two similar curves that resemble a parabola. Hyperbola has two fixed points which can be shown in the picture, are known as foci or focus. When we join the foci or focus using a line segment then its midpoint gives us centre. Hence, this line segment is known as the transverse axis.

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