Let $\displaystyle f:\mathbb{R} \rightarrow \mathbb{R}$ be continuous at $\displaystyle c$ and let $\displaystyle f(c)>0$. How would you show that there is a neighborhood $\displaystyle V_{\delta}(c)$ of $\displaystyle c$ such that if $\displaystyle x \in V_{\delta}(c)$, then $\displaystyle f(x) > 0$