Exams › JEE Main › Maths
Let f: (0, infinity) -> R be differentiable with f'(x) = 2 - f(x)/x for all x > 0 and f(1) != 1. Which statement is true?
- lim x->0+ f'(1/x) = 1
- lim x->0+ x f(1/x) = 2
- lim x->0+ x² f'(x) = 0
- |f(x)| <= 2 for all x in (0, 2)
Correct answer: lim x->0+ f'(1/x) = 1
Solution
f(x) = x + C/x, so f'(t) = 1 - C/t²; with t = 1/x -> infinity as x -> 0+, f'(1/x) -> 1.
Related JEE Main Maths questions
- If √(1-x²ⁿ)+√(1-y²ⁿ)=a(xⁿ-yⁿ), then the value of (√(1-x²ⁿ) dy)/(√(1-y²ⁿ) dx) is
- For a curve that passes through the point (4, 0), the slope is governed by
dy/dx = y/x + 5x/((x + 2)(x − 3)).
If the point (5, a) lies on this curve, what is the value of a?
- Which differential equation represents the family of all conics whose axes are aligned with the coordinate axes?
- Find the equation of the curve that satisfies (xy - x²) (dy)/(dx) = y² and passes through the point (-1, 1).
- For the differential equation y = y/x + x/y, if its general solution is written as y = x / log|Cx|, then the function φ(x/y) is
- For the differential equation dy/dx = [y f'(x) − y²]/f(x), where f(x) is a specified function, the solution is
⚔️ Practice JEE Main Maths free + battle 1v1 →