NTA Abhyas JEE Main2020MathematicsParabolaPractice
The set of points on the axis of the parabola y 2 - 2 y - 4 x + 5 = 0 from which all the three normals drawn to the parabola are real and distinct, is
Options
- Ax , 1 : x > 3
- Bx , - 1 : x ≥ 1
- Cx , 3 : x ≥ 1
- Dx , - 3 : x ≥ 3
Correct answer
A. x , 1 : x > 3
Step-by-step solution
Given equation of the parabola can be rewritten as ( y - 1 ) 2 = 4 ( x - 1 ) Axis of the parabola is y = 1 , equation of normal is y - 1 = m x - 1 - 2 m - m 3 Let ( h , 1 ) is a point on its axis, then 0 = m h - 1 - 2 m - m 3 ⇒ m 2 = h - 3 ⇒ h > 3 for real & distinct values of m