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JEE Mains · Maths · STD 12 - 5. continuity and differentiation

यदि \(f(x)\), अंतराल \((0, \infty)\) में एक ऐसा अवकलनीय फलन है कि \(f(1)=1\) तथा प्रत्येक \(x>0\) के लिए, \(\lim _{t \rightarrow x} \frac{t^{2} f(x)-x^{2} f(t)}{t-x}=1\) है, तो \(f(3 / 2)\) बराबर है

  1. A \(\frac {23}{18}\)
  2. B \(\frac {13}{6}\)
  3. C \(\frac {25}{9}\)
  4. D \(\frac {31}{18}\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(\frac {31}{18}\)

Step-by-step Solution

Detailed explanation

\(\lim_{t \to x} \frac{t^2f(x) - x^2f(t)}{t - x} = \lim_{t \to x} \left[ f(x)\frac{t^2 - x^2}{t - x} - x^2\frac{f(t) - f(x)}{t - x} \right]\) \(= f(x)(2x) - x^2f'(x)\) \(2xf(x) - x^2f'(x) = 1\) \(x^2f'(x) - 2xf(x) = -1\) \(\frac{f'(x)}{x^2} - \frac{2f(x)}{x^3} = -\frac{1}{x^4}\)…
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