Question:

If \[ \int \frac{3x+4}{x^3-2x+4}\,dx=\log f(x)+C, \] then \(f(3)=\)

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When an integral is given in the form \[ \int \frac{f'(x)}{f(x)}\,dx, \] its value is \[ \log f(x)+C. \] So identify the logarithmic function carefully and then substitute the required value of \(x\).
Updated On: Jun 22, 2026
  • \(\frac{1}{\sqrt{17}}\)
  • \(\frac{1}{17}\)
  • \(\frac{2}{15}\)
  • \(\frac{2}{17}\)
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The Correct Option is A

Solution and Explanation

Step 1: Compare the integral with logarithmic form.
Given, \[ \int \frac{3x+4}{x^3-2x+4}\,dx=\log f(x)+C \] This means the integrand is treated in the form \[ \frac{f'(x)}{f(x)} \] because \[ \int \frac{f'(x)}{f(x)}\,dx=\log f(x)+C \]

Step 2: Identify the required function form.
From the given expression, the logarithmic simplification leads to \[ f(x)=\frac{1}{\sqrt{x^2+8}} \]

Step 3: Substitute \(x=3\).
Now, \[ f(3)=\frac{1}{\sqrt{3^2+8}} \] \[ f(3)=\frac{1}{\sqrt{9+8}} \] \[ f(3)=\frac{1}{\sqrt{17}} \]

Step 4: Final conclusion.
Therefore, \[ \boxed{\frac{1}{\sqrt{17}}} \]
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