% Fichier ex4.4.8-4.tex - Ch. Rolland/O Reilly France
\documentclass{article}
\usepackage[latin1]{inputenc}
\begin{document}
\begin{eqnarray}
\lefteqn{z_1+z_2+\cdots+z_n = }
\nonumber \\
& & x_1y_1+x_2y_2 \nonumber\\
& & +x_3y_3+\cdots+x_ny_n
\end{eqnarray}
\end{document}
