NCERT Class XI Mathematics - Conic Sections - Solutions
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Question : 60
Total: 71
Foci (±4, 0), the latus rectum is of length 12.
Solution:
Here foci are (±4, 0) which lie on x-axis.
So the equation of the hyperbola in standard form is
−
= 1.
Now Foci are (±4, 0) ⇒ c = 4.
Length of latus rectum is
= 12 ⇒ b 2 = 6a
We know thatc 2 = a 2 + b 2
∴( 4 ) 2 = a 2 + 6a ⇒ a 2 + 6a – 16 = 0
⇒ (a + 8)(a – 2) = 0
⇒ a = 2 (Since a = – 8 is not possible)
∴a 2 = 4 ⇒ b 2 = 6 × 2 = 12
Thus, required equation of hyperbola is
−
= 1.
So the equation of the hyperbola in standard form is
Now Foci are (±4, 0) ⇒ c = 4.
Length of latus rectum is
We know that
∴
⇒ (a + 8)(a – 2) = 0
⇒ a = 2 (Since a = – 8 is not possible)
∴
Thus, required equation of hyperbola is
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