[Tex/LaTex] How to align a split environment to the left

Question

Consider:

\begin{flalign}
\begin{split}
\text{Consider a function}:   \pi:N \times N \rightarrow N  & \\
           \text{such that}:  &  \\
    \pi (k_{1},k_{2}):= \frac{1}{2}(k_{1}+k_{2})(k_{1}+k_{2}+1)+k_{2}  \forall \left ( k_{1},k_{2} \right )\epsilon N^{2} & \\ 
\end{split} 
\end{flalign}

Answer 1

If it fits what you want, you could use:

\noindent Consider a function:\quad  $\displaystyle \pi\colon \mathbb{N} \times \mathbb{N} \rightarrow \mathbb{N}$\\
such that:
\begin{equation}
  \pi (k_{1},k_{2}) := \frac{1}{2}(k_{1}+k_{2})(k_{1}+k_{2}+1)+k_{2}  \forall \left ( k_{1},k_{2} \right )\in \mathbb{N}^{2}  \label{eq:3}
\end{equation}