2

I am trying to align my cases with other lines in my align environment but have had no luck thus far. Can you tell me how to align all these lines:

enter image description here

Here is my code:

\documentclass[11pt]{article}


\usepackage[framemethod=default]{mdframed}
\usepackage{mathtools}
\usepackage[most]{tcolorbox}
\tcbset{myformula/.style={
  arc=0pt,
  outer arc=0pt,
  colback=blue!10,
  colframe=green,
  boxrule=0.8pt,
  left=2pt,
  right=2pt,
  highlight math style={
    arc=0pt,
    outer arc=0pt,
    colback=green,
    colframe=red.
    }
  }
}



\begin{document}

\begin{tcolorbox}[ams align, myformula]
Q(z) & =  a_{n}z^{n} + a_{n-1}z^{n-1} + \dots + a_{2}z^{2} + a_{1}z^{1} + a_{0} = 0
\intertext{The conditions for stability are}\\
Q(1) & >  0
\intertext{and:}
\begin{dcases}
Q(-1) & >  0 \quad \text{if $n$ is even}\\
Q(-1) & <  0\quad \text{if $n$ is odd}
\end{dcases}
\end{tcolorbox}

\end{document}
2
  • The & in dcases separates the formula from its description, so it should be Q(-1)>0 & \text{if $n$ is even}. Aside from this, are you sure you want to align those three formulas? I have no doubt I wouldn't.
    – egreg
    Jun 1, 2017 at 6:13
  • Why did you add a double backslash after the first \intertext?
    – Bernard
    Jun 1, 2017 at 7:29

2 Answers 2

6
\begin{tcolorbox}[ams align, myformula]
    & Q(z) =  a_{n}z^{n} + a_{n-1}z^{n-1} + \dots + a_{2}z^{2} + a_{1}z^{1} + a_{0} = 
    0
    \intertext{The conditions for stability are}
    & Q(1) >  0
    \intertext{and:}
    & \begin{dcases}
        Q(-1) & >  0 \quad \text{if $n$ is even}\\
        Q(-1) & <  0\quad \text{if $n$ is odd}
    \end{dcases}
\end{tcolorbox}

enter image description here

3

A… well, not-so-slight (:-) improvement on Herbert’s answer:

\documentclass[11pt]{article}


\usepackage[framemethod=default]{mdframed}
\usepackage{mathtools}
\usepackage[most]{tcolorbox}
\tcbset{myformula/.style={
  arc=0pt,
  outer arc=0pt,
  colback=blue!10,
  colframe=green,
  boxrule=0.8pt,
  left=2pt,
  right=2pt,
  highlight math style={
    arc=0pt,
    outer arc=0pt,
    colback=green,
    colframe=red.
    }
  }
}



\begin{document}

\begin{tcolorbox}[ams align, myformula]
    & Q(z) = a_{n}z^{n} + a_{n-1}z^{n-1} + \dots + a_{2}z^{2} + a_{1}z^{1} + a_{0} 
        = 0
    \intertext{The conditions for stability are}
    & Q(1) >  0
    \intertext{and:}
    & \begin{dcases*}
        Q(-1) > 0, & if $n$ is even;\\
        Q(-1) < 0, & if $n$ is odd.
    \end{dcases*}
\end{tcolorbox}
\end{document}

The output is:

Output of the code

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