f ″ ( 10 ) = − 2 ( 1 + 10 ) 3 = − 2 11 3 < 0. {\displaystyle f''(10)={\frac {-2}{(1+10)^{3}}}={\frac {-2}{11^{3}}}<0.}
Therefore, the tangent line as a linear approximation is an overestimate of f ( x ) {\displaystyle f(x)} .
