NCERT Class XI Mathematics - Conic Sections - Solutions

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Question : 61
Total: 71
Vertices (±7, 0), e =
4
3
Solution:  
Here vertices are (±7, 0) which lie on x-axis.
So, the equation of hyperbola in standard form is
x2
a2
y2
b2
= 1.
∴ Vertices are (±7, 0) ⇒ a = 7
Now, e =
4
3
c
a
=
4
3
c
7
=
4
3
⇒ c =
28
3

We know that c2 = a2+b2
(
28
3
)
2
= (7)2+b2b2 =
784
9
49
=
343
9
.
Thus required equation of hyperbola is
x2
(7)2
y2
343
9
= 1 ⇒
x2
49
9y2
343
= 1.
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