If is a tangent to both the parabolas, and , then is equal to:
- (A)-32
- (B)-128✓ Correct
- (C)-64
- (D)128
Answer: (B)
Solution
A tangent of slope to is ; matching gives , so and the line is , i.e. . Substituting into gives , and tangency needs a zero discriminant: , so . The non-trivial root gives .
JEE Main · 2020 · 07 Jan 2020 · Shift 1 · Single correct option