KVPY2016MathematicsApplication of Derivatives
Let f ( x ) be a non-negative differentiable function on [0, ) such that f (0)=0 and f ( x ) 2 f ( x ) for all x >0 . Then, on [0, )
Options
- Af ( x ) is always a constant function
- Bf ( x ) is strictly increasing
- Cf ( x ) is strictly decreasing
- Df ^ ( x ) changes sign
Correct answer
A. f ( x ) is always a constant function
Step-by-step solution
f ^ ( x ) 2 f ( x ) f ^ ( x ) e ^ -2 x 2 f ( x ) e ^ -2 x d dx ( f ( x ) e ^ -2 n ) 0 ~g ( x )= f ( x ) e ^ -2 x is non-Increasing function x 0 ~g ( x ) g (0) f ( x ) e ^ -2 x f (0) e ⁻⁰ f ( x ) e ^ -2 x 0 f ( x ) 0 but given f ( x ) is not negative f ( x )=0 Constant function