TeX source:

\frac{1}{2} m v_{\mathrm{i}}^{2}+m g h_{\mathrm{i}}+\frac{1}{2} k x_{\mathrm{i}}^{2}=\frac{1}{2} m v_{\mathrm{f}}^{2}+m g h_{\mathrm{f}}+\frac{1}{2} k x_{\mathrm{f}}^{2}