JEE Main20206 Sep 2020Morning ShiftMathematicsParabolaActual
Let L 1 be a tangent to the parabola y 2 = 4 ( x + 1 ) and L 2 be a tangent to the parabola y 2 = 8 ( x + 2 ) such that L 1 and L 2 intersect at right angles. Then L 1 and L 2 meet on the straight line:
Options
- Ax + 3 = 0
- B2x + 1 = 0
- Cx + 2 = 0
- Dx + 2y = 0
Correct answer
A. x + 3 = 0
Step-by-step solution
Let tangent of y 2 = 4 ( x + 1 ) be L 1 : t 1 y = ( x + 1 ) + t 1 2 and tangent of y 2 = 8 ( x + 2 ) be L 2 : t 2 y = ( x + 2 ) + 2 t 2 2 L 1 ⊥ L 2 1 t 1 · 1 t 2 = - 1 t 1 t 2 = - 1 t 2 × ( i ) - t 1 × ( i i )    ⇒    x + 3 = 0