Let the hyperbola H: x^2 a^2- y^2 b^2=1 pass through the point (2√2,-2√2). A parabola is drawn whose focus is same as the focus of H with positive…
JEE Main 2022 — Mathematics Coordinate Geometry
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Let the hyperbola H:a2x2−b2y2=1 pass through the point (22,−22). A parabola is drawn whose focus is same as the focus of H with positive abscissa and the directrix of the parabola passes through the other focus of H. If the length of the latus rectum of the parabola is e times the length of the latus rectum of H, where e is the eccentricity of H, then which of the following points lies on the parabola?
Official previous-year question
Held on 28 Jul 2022 · Verified 6 Jul 2026.
Options
A
(23,32)
B
(33,−62)
C
(3,−6)
D
(36,62)
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Solution
Given,
H:a2x2−b2y2=1
So coordinates of foci will be : S(ae,0),S′(−ae,0)
Now foot of directrix of parabola will be (−ae,0)
Also focus of parabola is which is same as focus of H will be (ae,0)
Now, semi latus rectum of parabola =∣SS′∣=2ae
Given, 4ae=e(a2b2)
⇒b2=2a2...(1)
Also given, (22,−22) lies on H:a2x2−b2y2=1
⇒a2(22)2−b2(22)2=1
⇒a21−b21=81...(2)
Now from equation (1)&(2) we get,
a2=4,b2=8
∵b2=a2(e2−1)
∴e=3
So, the equation of parabola is y2=4×(ae)x⇒y2=83x
So, only (33,−62) will satisfy the parabola y2=83x
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