[Tex/LaTex] Left-aligning equations

Question

How do I left-align selective equation blocks, i.e. not centered ?

I know how to do it for ALL equation blocks in the document setting

\usepackage[fleqn]{amsmath}
\setlength{\mathindent}{0pt}

in the preamble, but I only want to do this for some equation blocks.

\documentclass[pdftex,12pt,a4paper,english,dutch,leqno]{article}
\usepackage[top=1cm,right=1cm,bottom=1cm,left=1.5cm,noheadfoot]{geometry}
\usepackage{babel}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage[dvipsnames,table]{xcolor}
\usepackage{color}
\definecolor{vanillegeel}{RGB}{255,240,216}
\usepackage{empheq}

\begin{document}

De raaklijn aan $(x_{0},f(x_{0}))$ wordt algemeen bepaald met :
\begin{empheq}[box={\fboxsep=3pt\colorbox{vanillegeel}}]{align*}
\textnormal{$\begin{cases}z=f(x)\text{ is continu in }x_{0}\text{.}\\
f'(x_{0})=0\text{ : }z=f(x_{0})\text{ is de horizontale raaklijn.}\\
\lim_{x\to x_{0}} f'(x)=\pm\infty\text{ : }x=x_{0}\text{ is de verticale raaklijn.}\\
f'(x_{0})\in\mathbb{R}_{0}\text{ : }z-f(x_{0})=f'(x_{0})\cdot(x-x_{0})\text{ is de raaklijn.\hspace{-12pt}}\end{cases}$}\end{empheq}

\end{document}

Answer 1

Don't use align*.

De raaklijn aan $(x_{0},f(x_{0}))$ wordt algemeen bepaald met:
\begin{flushleft}
\colorbox{vanillegeel}{%
$\displaystyle
\begin{cases}
z=f(x) \text{ is continu in } x_{0}.
\\
f'(x_{0})=0 \text{ : } z=f(x_{0}) \text{ is de horizontale raaklijn.}
\\
\lim_{x\to x_{0}} f'(x)=\pm\infty \text{ : } x=x_{0} \text{ is de verticale raaklijn.}
\\
f'(x_{0})\in\mathbb{R}_{0} \text{ : } z-f(x_{0})=f'(x_{0})\cdot(x-x_{0})
  \text{ is de raaklijn.}
\end{cases}
$\kern-\nulldelimiterspace\kern-2\arraycolsep}
\end{flushleft}