Q175 / 270 · NDA 2017 (Phase 1) · Mathematics

If $S=\left(x: x^2+1=0, x\right.$ is real $)$, then $S$ is

  • A
    $\{-1\}$
  • B
    $\{0\}$
  • C
    $\{1\}$
  • Correct answer
    D
    an empty set

Solution

$\begin{aligned} & S=\left\{x: x^2+1=0, x: 5 \text { real }\right\} \\ & x^2+1=0 \Rightarrow x^2=-1 \Rightarrow x=\sqrt{-1} \rightarrow \text { complex number } \end{aligned}$ No real numbers. So, S is empty set

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

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