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Question: Answered & Verified by Expert
If $f(x)=4 x^3+3 x^2+3 x+4$, then $x^3 f\left(\frac{1}{x}\right)$ is
MathematicsFunctionsJEE Main
Options:
  • A $f(-x)$
  • B $\frac{1}{f(x)}$
  • C $\left(f\left(\frac{1}{x}\right)\right)^2$
  • D $f(x)$
Solution:
2816 Upvotes Verified Answer
The correct answer is: $f(x)$
$\begin{aligned} x^3 f\left(\frac{1}{x}\right)= & x^3\left[\frac{4}{x^3}+\frac{3}{x^2}+\frac{3}{x}+4\right] \\ & =4+3 x+3 x^2+4 x^3=f(x)\end{aligned}$

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