NTA Abhyas JEE Main2020MathematicsParabolaPractice
Let the focus S of the parabola y 2 = 8 x lie on the focal chord P Q of the same parabola. If the length Q S = 3 units, then the ratio of length P Q to the length of the latus rectum of the parabola is
Options
- A2 5
- B4 5
- C5 4
- D9 8
Correct answer
D. 9 8
Step-by-step solution
For the focal chord P Q , we know that, P S , 4 , S Q are in H.P. ⇒ 1 P S , 1 4 , 1 3 are in A.P. ⇒ 1 P S = 2 4 - 1 3 = 1 6 ⇒ P S = 6 ⇒ P Q = 6 + 3 = 9 ⇒ P Q length of l a t u s re c t u m = 9 8