Question:

Let \(f: S \to S\) where \(S = (0, \infty)\) be a twice differentiable function such that \(f(x+1) = xf(x)\). If \(g: S \to \mathbb{R}\) be defined as \(g(x) = \log_e f(x)\), then the value of \(|g''(5) - g''(1)|\) is equal to :

Show Hint

Take logs to get \(g(x+1) = \log_e x + g(x)\), then differentiate twice.
Updated On: Nov 4, 2026
  • 1
  • \(\frac{187}{144}\)
  • \(\frac{197}{144}\)
  • \(\frac{205}{144}\)
Show Solution
collegedunia
Verified By Collegedunia

The Correct Option is D

Solution and Explanation

\(f(x+1) = xf(x)\Rightarrow g(x+1) = \log_e x + g(x)\).
Differentiate twice: \(g''(x+1) = -\frac{1}{x^2} + g''(x)\), i.e. \(g''(x+1) - g''(x) = -\frac{1}{x^2}\).
Put \(x = 1,2,3,4\) and add: \(g''(5) - g''(1) = -\left(1 + \frac{1}{4} + \frac{1}{9} + \frac{1}{16}\right) = -\frac{144 + 36 + 16 + 9}{144} = -\frac{205}{144}\).
\(|g''(5) - g''(1)| = \frac{205}{144}\).
Answer: (4) \(\frac{205}{144}\)
Was this answer helpful?
0
0