Typesetting an optimisation problem

Just change align into alignat:

\documentclass{report}
\usepackage{amsmath}

\newcommand{\norm}[1]{\lVert#1\rVert_2}

\begin{document}

\begin{subequations}
\begin{alignat}{2}
&\!\min_{x}        &\qquad& \norm{f(x)}^2\label{eq:optProb}\\
&\text{subject to} &      & \alpha \geq 0,\label{eq:constraint1}\\
&                  &      & \beta \geq 0.\label{eq:constraint2}
\end{alignat}
\end{subequations}

\end{document}

I rather use alignat because allows aligning the equals\inequality signs also:

\begin{alignat}{3}
\max_x              &\quad&  z = \sum_{j=1}^n c_i x_j  &&          & \\
\text{subject to: } &\quad&  \sum_{j=1}^n a_{ij} x_j   && \leq b_i &\quad \forall i=1,m\\
                    &\quad&  x_j                       && \geq 0   &\quad \forall j=1,n
\end{alignat}

The numbers appear by default.