problem follows, "let y be the linearisation of the function $\displaystyle f(x) = \frac{1}{x}$ at $\displaystyle x = 2$.

If $\displaystyle \Delta x = 0.1$ then $\displaystyle \Delta y = ?$

This is what I get.

$\displaystyle

\begin{array}{l}

\Delta y = f(x + \Delta x) - f(x) \\

= f(2 + 0.1) - f(2) \\

= \frac{1}{{2.1}} - \frac{1}{2} \approx - 0.0238 \\

\end{array}

$

However answer is give as being -0.025. Rounding my above answer only give -0.024

Have I done something wrong?