LaTeX Forum

\documentclass[12pt]{scrreprt} 
\usepackage[fleqn]{amsmath}
\usepackage{amssymb}

\usepackage[norndcorners,customcolors,nofill]{hf-tikz}
\hfsetbordercolor{gray}

\begin{document} 
\begin{align*} 
\max_{w} U & =w^{T}_{M}\Pi+\frac{\delta}{2}(w^{T}_{M})\Sigma w_{M}\\ 
\Leftrightarrow \frac{\partial U}{\partial w_{M}} & =\Pi-\delta \Sigma w_{M}=0\\[.5\baselineskip] 
\tikzmarkin{wM}(0.15,-0.4)(-0.05,0.6)\Leftrightarrow w_{M} & = (\delta\Sigma)^{-1}\Pi\tikzmarkend{wM} 
\end{align*} 
\end{document}

\documentclass[12pt,oneside]{scrreprt}
\usepackage[latin1]{inputenc}
\usepackage[ngerman,english]{babel}
\usepackage[left=6cm,right=2cm, top=3cm, bottom=3cm]{geometry} %layout
\usepackage[fleqn]{amsmath} %Math
\usepackage{amsthm}

\usepackage{amstext}
\usepackage{amsfonts}
\usepackage{mathrsfs}
\usepackage{amssymb}
\usepackage{acronym}
\begin{document}
\begin{eqnarray*}
\max_{w} U & = & w^{T}_{M}\Pi+\frac{\delta}{2}(w^{T}_{M})\Sigma w_{M}\\
\Leftrightarrow \frac{\partial U}{\partial w_{M}} & = &\Pi-\delta \Sigma w_{M}=0\\
\Leftrightarrow w_{M} & = & (\delta\Sigma)^{-1}\Pi
\end{eqnarray*}
\end{document}

w_{M} & = & (\delta\Sigma)^{-1}\Pi