\input{_preamble}
\begin{document}
    \myeqs{
        \mu_{g,h}^{(k)}(u)
        =
        \begin{cases}
            0 & \text{if}\quad u_{g+h+1}^{(k)} = u_{g}^{(k)}\\[2mm]
            \frac{u-u_g^{(k)}}{u_{g+h+1}^{(k)}-u_g^{(k)}} & \text{else}
        \end{cases}
    }
\end{document}