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Define a function \(f : [0, 1] \to \mathbf{R}\) as \(f(x) = x^{2} + e^{x} - 2\). Then :

  • A.\(f(x) = 0\) has no solution in [0, 1]
  • B.\(f'(x) = 0\) has a solution in [0, 1]
  • C.\(f\) is increasing
  • D.\(f\) is not one-one

Answer: C

The correct statement is \(f\) is increasing.

\[ f'(x) = 2x + e^{x} \]

On [0, 1] both terms are non-negative and \(e^{x} \ge 1\), so \(f'(x) \gt 0\) throughout and \(f\) is strictly increasing.

That rules out the others. \(f'\) never vanishes on [0, 1], and a strictly increasing function is one-one. Also \(f(0) = -1 \lt 0\) and \(f(1) = e - 1 \gt 0\), so by the intermediate value theorem \(f(x) = 0\) does have a root in [0, 1].

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