Q44 / 90 · JEE Main 2022 (28 Jul Shift 2) · Mathematics

Let the hyperbola H:x2a2-y2 b2=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?

  • A
    23,32
  • Correct answer
    B
    33,-62
  • C
    3,-6
  • D
    36,62

Solution

Given,

H: x2a2-y2 b2=1

So coordinates of foci will be : Sae,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=e2b2a

⇒b2=2a2     ...1

Also given, 22,-22 lies on H: x2a2-y2 b2=1

⇒222a2-222 b2=1

⇒1a2-1 b2=18   ...2

Now from equation 1 & 2 we get,

a2=4, b2=8

∵b2=a2e2-1

∴  e=3

So, the equation of parabola is y2=4×aex⇒y2=83x

So, only 33,-62 will satisfy the parabola y2=83x

Hence, the correct answer is option: 'B'.

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