Hàm số y = x / x − 2 có đạo hàm cấp hai là:

\[\begin{array}{*{20}{l}}{y' = \frac{{1.\left( {x - 2} \right) - x.1}}{{{{\left( {x - 2} \right)}^2}}} = \frac{{ - 2}}{{{{\left( {x - 2} \right)}^2}}}}\\{y'' = \frac{{{{\left( { - 2} \right)}^\prime }{{\left( {x - 2} \right)}^2} - \left( { - 2} \right).{{\left( {{{\left( {x - 2} \right)}^2}} \right)}^\prime }}}{{{{\left( {x - 2} \right)}^4}}} = \frac{{4\left( {x - 2} \right)}}{{{{\left( {x - 2} \right)}^4}}} = \frac{4}{{{{\left( {x - 2} \right)}^3}}}}\end{array}\]