# Math Help - Parentheses spanning multiple lines?

1. ## Parentheses spanning multiple lines?

How can I open a bracket on 1 line, then close it on the next? If I try something like

\begin{multline}
a + \left[ x-a \\
\left[x-b\right]\right]
\end{multline}

it gives me an error saying I forgot to close the \right] on the first line.

2. Originally Posted by scorpion007
How can I open a bracket on 1 line, then close it on the next? If I try something like

\begin{multline}
a + \left[ x-a \\
\left[x-b\right]\right]
\end{multline}

it gives me an error saying I forgot to close the \right] on the first line.
Something like this?

$a+\left[\begin{array}{l}x-a\\\left[x+b\right]\end{array}\right]$ or $a+\!\begin{array}{l}\left[x-a\right.\\\,\left.\left[x+b\right]\right]\end{array}$ or $\begin{array}{r}a+\left[x-a\right.\,\,\,\\ \left.\left[x+b\right]\right]\end{array}$

3. Ah, yes, thank you, like the last one.

What is this "\left." you used? Is it like an invisible placeholder to balance the parens?

4. Originally Posted by scorpion007
Ah, yes, thank you, like the last one.

What is this "\left." you used? Is it like an invisible placeholder to balance the parens?
Yes it is!

5. Originally Posted by scorpion007
How can I open a bracket on 1 line, then close it on the next? If I try something like

\begin{multline}
a + \left[ x-a \\
\left[x-b\right]\right]
\end{multline}

it gives me an error saying I forgot to close the \right] on the first line.
\begin{multline}
a + \left[ x-a \right. \\
\left. \left[x-b\right]\right]
\end{multline}

CB