\documentclass{amsart}
\begin{document}
\[
\prod_{k=0,\ k\neq i}^{n}
\frac{x-c_{k}}{c_{i}-c_{k}}
\]
\end{document}
I would like to make the k \neq i,
which is next to k=0, parallel to k = 0.
I tried \\, \limits, and \begin{align*} ... \end{align*}, but somehow I did not get the desired result out of the actions.
amsartdocumentclass. Then, you don't need to writeusepackage{amsart}in the preamble. – Merzong Jun 19 '15 at 04:08\documentclass{amsart}at the start of the code block. – Mico Jun 19 '15 at 04:13