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QJEEM23Ma4131: JEE Main 2023 Mathematics - Class 12 JEEM23Ma4131 Solution: For the differentiable function , let , then is equal to

For the differentiable function f:R−{0}→Rf: \mathbb{R}-\{0\} \rightarrow \mathbb{R} , let 3f(x)+2f(1x)=1x−103 f(x)+2 f\left(\frac{1}{x}\right)=\frac{1}{x}-10 , then ∣f(3)+f′(14)∣\left|f(3)+f^{\prime}\left(\frac{1}{4}\right)\right| is equal to

Multiple Choice Options

  • A 13
  • B 295\frac{29}{5}
  • C 335\frac{33}{5}
  • D 7

Step-by-Step Verified Solution

  1. Given the equation: 3f(x)+2f(1x)=1x−103f(x) + 2f\left(\frac{1}{x}\right) = \frac{1}{x} - 10

  2. Replace xx with 1x\frac{1}{x} in the original equation:
    3f(1x)+2f(x)=x−103f\left(\frac{1}{x}\right) + 2f(x) = x - 10

  3. Now, we have two equations:

3f(x)+2f(1x)=1x−103f(x) + 2f\left(\frac{1}{x}\right) = \frac{1}{x} - 10

3f(1x)+2f(x)=x−103f\left(\frac{1}{x}\right) + 2f(x) = x - 10

  1. By adding the two equations, we can find f(x)f(x) :

5f(x)=3x−2x−105f(x) = \frac{3}{x} - 2x - 10

  1. Now, let's differentiate both sides with respect to xx :

5f′(x)=−3x2−25f'(x) = -\frac{3}{x^2} - 2

  1. Now, we can find the values for f(3)f(3) and f′(14)f'\left(\frac{1}{4}\right) :

f(3)=15(1−6−10)=−3f(3) = \frac{1}{5}(1 - 6 - 10) = -3

f′(14)=15(−48−2)=−10f'\left(\frac{1}{4}\right) = \frac{1}{5}(-48 - 2) = -10

  1. Finally, calculate the expression we are interested in :

∣f(3)+f′(14)∣=∣−3−10∣=13\left|f(3) + f'\left(\frac{1}{4}\right)\right| = \left|-3 - 10\right| = 13

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