Question

Axis of a parabola lies along x – axis. If its vertex and focus are at distance 2 and 4 respectively from the origin, on the positive x – axis then which of the following points does not lie on it? (A) (5, 2√6) (B) (8, 6)
(C) (6, 4√2) (D) (4, –4)
[JEE Main 2019]

Answer 1

Answer:

Please see the attachment

Answer 2

(8, 6) doesn't lies on parabola

•let equation of required parabola

be (y-s)² = 4a(x-q)

•where (q,s) are coordinates of

verex.

•Axis of a parabola lies along x -axis

Vertex is 2 units away from origin

position of vertex is (2,0)

•Focus is 4 units away from origin

i.e. focus is at (0,4)

focal length i.e. a = 4-2 = 2units

•hence equation of parabola is

(y-0)² = 4(2)(x-2)

y² = 8(x-2) __________(1)

•On putting all the coordinates we

found that (8, 6) doesn't lies on

parabola .