JEE Main202116 Mar 2021Morning ShiftMathematicsParabolaActual
If the three normals drawn to the parabola, y 2 = 2 x pass through the point a , 0 , a ≠ 0 , then a must be greater than :
Options
- A1 2
- B- 1 2
- C- 1
- D1
Correct answer
D. 1
Step-by-step solution
Let the equation of the normal be y = m x - 2 a m - a m 3 Here 4 a = 2 a = 1 2 y = m x - m - 1 2 m 3 It passes through A ( a ,   0 ) then 0 = a m - m - 1 2 m 3 m = 0 , m 2 - 2 ( a - 1 ) = 0 For real values of m 2 ( a - 1 ) > 0 ⇒ a > 1