The question is the following:
Let $f$ be a polynomial of the ring $R[x_1, \ldots, x_n]$, with $R$ any ring, and let $\mathrm{cont}(f)$ be the ideal generated by the coefficients of $f$. Why if $\mathrm{cont}(f)$ contains a non-zerodivisor of $R$, then $f$ is a non-zerodivisor of $R[x_1, \ldots, x_n]$?