Medium MCQ +4 / -1 PYQ · JEE Mains 2024

Let $f: \mathbf{R}-\left\{\frac{-1}{2}\right\} \rightarrow \mathbf{R}$ and $g: \mathbf{R}-\left\{\frac{-5}{2}\right\} \rightarrow \mathbf{R}$ be defined as $f(x)=\frac{2 x+3}{2 x+1}$ and $g(x)=\frac{|x|+1}{2 x+5}$. Then, the domain of the function fog is :

  1. A $\mathbf{R}-\left\{-\frac{7}{4}\right\}$
  2. B $\mathbf{R}$
  3. C $\mathbf{R}-\left\{-\frac{5}{2},-\frac{7}{4}\right\}$
  4. D $\mathbf{R}-\left\{-\frac{5}{2}\right\}$ Correct answer

Solution

<p>$$\begin{aligned} & f(x)=\frac{2 x+3}{2 x+1} ; x \neq-\frac{1}{2} \\ & g(x)=\frac{|x|+1}{2 x+5}, x \neq-\frac{5}{2} \end{aligned}$$</p> <p>Domain of $f(g(x))$</p> <p>$f(g(x))=\frac{2 g(x)+3}{2 g(x)+1}$</p> <p>$x \neq-\frac{5}{2}$ and $\frac{|x|+1}{2 x+5} \neq-\frac{1}{2}$</p> <p>$x \in R-\left\{-\frac{5}{2}\right\}$ and $x \in R$</p> <p>$\therefore$ Domain will be $\mathrm{R}-\left\{-\frac{5}{2}\right\}$</p>

About this question

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

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