how to code left facing bracket of values with single value to its right?

Question

How can I make a vector in this form?

Answer 1

You can do that in two ways: either with the mathtools package (needless to load amsmath) or with the blkarray package. Math tools defines rcases and drcases environments (the latter is the displaystyle version of the former):

\documentclass{article}
\usepackage{mathtools}
\usepackage{blkarray}

\begin{document}

\[ \begin{rcases} -1 \\ \hphantom{-} \vdots \\ -1 \end{rcases}m \qquad
 \begin{blockarray}[t]{c \Right{\}}{\,$ m $}}-1 \\ \hphantom{-} \vdots \\ -1 \end{blockarray} \]

\end{document}