[latexpage]
At first, we sample $f(x)$ in the $N$ ($N$ is odd) equidistant points around $x^*$:
\[
f_k = f(x_k),\: x_k = x^*+kh,\: k=-\frac{N-1}{2},\dots,\frac{N-1}{2}
\]
where $h$ is some step.
Then we interpolate points $\{(x_k,f_k)\}$ by polynomial
\begin{equation} \label{eq:poly}
P_{N-1}(x)=\sum_{j=0}^{N-1}{a_jx^j}
\end{equation}
Its coefficients $\{a_j\}$ are found as a solution of system of linear equations:
\begin{equation} \label{eq:sys}
\left\{ P_{N-1}(x_k) = f_k\right\},\quad k=-\frac{N-1}{2},\dots,\frac{N-1}{2}
\end{equation}
\[
f(x)=\int_1^{\infty}\frac{1}{x^2}\,\mathrm{d}x=1
\]
\[
E = mc^2
\]
\[
\frac{d}{dx} \left( x^2 \right) = 2x
\]
\[
\alpha, \beta, \gamma, \delta
\]
\[
\lim_{x \to \infty} \frac{1}{x} = 0
\]
\[
\alpha, \beta, \gamma, \delta
\]
\[
\binom{n}{k}
\]