\documentclass{article} \begin{document} \begin{equation} \lim_{x\to0}\frac{\sqrt{1+x} - 1}{x} = \lim_{x\to0}\frac{(\sqrt{1+x} - 1)(\sqrt{1+x} + 1)}{x(\sqrt{1+x} + 1)} = \lim_{x\to0}\frac{1}{\sqrt{1+x} + 1} = \frac{1}{2} \end{equation} \begin{equation} \frac{\partial^2 U}{\partial x^2} + \frac{\partial^2 U}{\partial y^2} = 0\quad \Longrightarrow\quad U_M = \frac{1}{4\pi}\oint\limits_\Sigma\frac{1}{r}\frac{\partial U}{\partial n} \,ds - \frac{1}{4\pi}\oint\limits_\Sigma\frac{\partial\frac{1}{r}}{\partial n} U\,ds \end{equation} \end{document}