eqnarray*Environment

How to write an unnumbered equation array#

\begin{eqnarray*} a &=& b+c \\ &=& d \end{eqnarray*}

How to break a long identity without numbers#

Starred form of the discouraged eqnarray environment.

\begin{eqnarray*} (a+b)^2 &=& a^2+2ab+b^2 \\ &=& a(a+2b)+b^2 \end{eqnarray*}