Medium MCQ +4 / -1 PYQ · JEE Mains 2025

Let $f(x)=\log _{\mathrm{e}} x$ and $g(x)=\frac{x^4-2 x^3+3 x^2-2 x+2}{2 x^2-2 x+1}$. Then the domain of $f \circ g$ is

  1. A $(0, \infty)$
  2. B $[1, \infty)$
  3. C $\mathbb{R}$ Correct answer
  4. D $[0, \infty)$

Solution

<p>$$\begin{aligned} & f(x)=\ln x \\ & g(x)=\frac{x^4-2 x^3+3 x^2-2 x+2}{2 x^2-2 x+1} \\ & D_g \in R \\ & D_f \in(0, \infty) \end{aligned}$$</p> <p>For $D_{f o g} \Rightarrow g(x)>0$</p> <p>$$\begin{aligned} & \frac{x^4-2 x^3+3 x^2-2 x+2}{2 x^2-2 x+1}>0 \\ & \Rightarrow x^4-2 x^3+3 x^2-2 x+2>0 \end{aligned}$$</p> <p>Clearly $\mathrm{x}<0$ satisfies which are included in option (1) only.</p>

About this question

Subject: Mathematics · Chapter: Sets, Relations and Functions · Topic: Sets and Operations

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