Q75 / 180 · KCET 2017 · Mathematics

Let \( f: R \rightarrow R \) be defined by \( f(x)=x^{4} \), then

  • A
    \( \mathrm{f} \) is one-one and onto
  • B
    \( \mathrm{f} \) may be one-one and onto
  • C
    \( \mathrm{f} \) is one-one but not onto
  • Correct answer
    D
    \( \mathrm{f} \) is neither one-one nor onto

Solution

Given that, $f: R \rightarrow R$ and $f(x)=x^{4}$ Since, $f\left(x_{1}\right)=f\left(x_{2}\right)$ $\Rightarrow x_{1}=\pm x_{2}$ So, $f(x)$ is not one-one function. Let $y=x^{4}$ $\Rightarrow x=\sqrt[4]{y}$ or $\Rightarrow y=\sqrt[4]{\chi}$ and $\Rightarrow \sqrt[4]{x} \notin R$ So, $f(x)$ is not onto function.

Hence, the correct answer is option: 'D'.

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