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TS EAMCET · Maths · Functions

If \(f: \mathbb{R} \rightarrow \mathbb{R}\) is defined by \(f(\mathrm{x})=2 \mathrm{x}+\sin \mathrm{x}, \mathrm{x} \in \mathrm{R}\), then \(f\) is

  1. A one-one and onto
  2. B one-one but not onto
  3. C onto but not one-one
  4. D neither one-one nor onto
Verified Solution

Answer & Solution

Correct Answer

(A) one-one and onto

Step-by-step Solution

Detailed explanation

\[ \begin{aligned} & f(x)=2 x+\sin x \\ & f^{\prime}(x)=2+\cos x>0 \end{aligned} \] \(\therefore f(x)\) is one-one. \(\because \quad \forall y \in f(x)\), there exist some \(x\) as there is a polynomial function \(2 x\). \(\therefore f(x)\) is onto.