Show that $\displaystyle f: A \rightarrow R^{m} $ is continuous at $\displaystyle x_0 $ iff for every $\displaystyle \epsilon > 0 $, there exist $\displaystyle \delta > 0 $ such that $\displaystyle || x-x_0 || \leq \delta $, we have $\displaystyle ||f(x)-f(x_0)|| \leq \epsilon $

So I can replace the definition < with $\displaystyle \leq $?