Q59 of 62 Page 11

Foci (± 3,0), the latus rectum is of length.


Since the foci are on x-axis, the equation of the hyperbola is of the form
= 1

Given: foci are (± 3,0), c = 3

and length of latus rectum = = 8

As b2 = 4a

We have c2 = a2 + b2

or 45 = a2 + 4a

or a2 + 4a – 45 = 0

or a2 + 9a – 5a - 45 = 0

or a(a + 9) –5(a – 9) = 0

or (a + 9) (a – 5) = 0

or a = -9 or a = 5)

since a cannot be negative, we take a = 5 and so b2 = 20.

Therefore, the equation of the required hyperbola is

= 1 ⇒ 4x2 – 5y2 = 100.

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