Cho hàm số f(x) xác định bởi \(% MathType!MTEF!2!1!+-
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% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x
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f\left( x \right) = \left\{ \begin{array}{l}
\frac{{\sqrt {{x^2} + 1} - 1}}{x}\,\,\,\left( {x \ne 0} \right)\\
0\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\left( {x = 0} \right)
\end{array} \right.\). Giá trị f’(0) bằng: