LaTeX Forum

\documentclass[twoside, a4paper, DIV=12, ngerman]{article}
\usepackage[T1]{fontenc}
\usepackage{babel}
\usepackage[utf8]{inputenc}
\usepackage{mathtools}
\begin{document}
\begin{equation}
\begin{split}
  & \frac{\partial H_{m,\textnormal{real}}(\rho_{m},T,a_i)}{\partial \rho_{m}}
  = \bigg(T \cdot a_1 - 2 \cdot a_2 - 3 \cdot \frac{a_3}{T}
     - 4 \cdot \frac{a_4}{T^2} - 5 \cdot \frac{a_5}{T^3}\bigg) \\
  &+ \bigg(2 \cdot T \cdot a_6 + 3 \cdot a_7 + 4 \cdot \frac{a_8}{T}\bigg)
    \cdot \rho_m + \bigg(3 \cdot T \cdot a_9 + 4 \cdot a_{10}\bigg)
    \cdot \rho_m^2 \\
  &+ (4 \cdot T \cdot a_{11} + 5 \cdot a_{12}) \cdot \rho_m^3
    + 6 \cdot \rho_m^4 a_{13} \\
  &+ \frac{1}{T^2} \cdot \rho_m \cdot \exp(-a_{20} \cdot \rho_m^2)
    \cdot \Bigl\{(5 - 2 \cdot a_{20} \cdot \rho_m^2) \cdot a_{14}
      + 2 \cdot (3 - a_{20} \cdot \rho_m^2) \\
  &\cdot \frac{a_{15}}{T} + (7 - 2 \cdot a_{20} \cdot \rho_m^2)
    \cdot \frac{a_{16}}{T^2} + \rho_m^2) \cdot \Bigl[(7 - 2 \cdot a_{20}
    \cdot \rho_m^2) \cdot a_{17} \\
  &+ 2 \cdot (4 - a_{20} \cdot \rho_m^2) \cdot \frac{a_{18}}{T}
    + (9 - 2 \cdot a_{20} \cdot \rho_m^2) \cdot \frac{a_{19}}{T^2} \Bigr]\Bigr\}
\end{split}
\end{equation}
\end{document}

\documentclass[twoside, a4paper, DIV=12, ngerman]{article}
\usepackage[T1]{fontenc}
\usepackage{babel}
\usepackage[utf8]{inputenc}
\usepackage{mathtools}
\begin{document}
\begin{align}
\begin{split}
& \frac{\partial H_{m,real}(\rho_{m},T,a_i)}{\partial \rho_{m}} = \bigg(T \cdot a_1 - 2 \cdot a_2 - 3 \cdot \frac{a_3}{T} - 4 \cdot \frac{a_4}{T^2} - 5 \cdot \frac{a_5}{T^3}\bigg) \\ &+ \bigg(2 \cdot T \cdot a_6 + 3 \cdot a_7 + 4 \cdot \frac{a_8}{T}\bigg) \cdot \rho_m + \bigg(3 \cdot T \cdot a_9 + 4 \cdot a_{10}\bigg) \cdot \rho_m^2 \\ &+ (4 \cdot T \cdot a_{11} + 5 \cdot a_{12}) \cdot \rho_m^3 + 6 \cdot \rho_m^4 a_{13} \\ &+ \frac{1}{T^2} \cdot \rho_m \cdot exp(-a_{20} \cdot \rho_m^2) \cdot \left\{(5 - 2 \cdot a_{20} \cdot \rho_m^2) \cdot a_{14} + 2 \cdot (3 - a_{20} \cdot \rho_m^2) \right. \\ &\cdot \left. \frac{a_{15}}{T} + (7 - 2 \cdot a_{20} \cdot \rho_m^2) \cdot \frac{a_{16}}{T^2} + \rho_m^2) \cdot \Big[(7 - 2 \cdot a_{20} \cdot \rho_m^2) \cdot a_{17} \right. \\ &+ \left. 2 \cdot (4 - a_{20} \cdot \rho_m^2) \cdot \frac{a_{18}}{T} + (9 - 2 \cdot a_{20} \cdot \rho_m^2) \cdot \frac{a_{19}}{T^2} \Big]\right\}
\end{split}
\end{align}
\end{document}