Answer
None.
Work Step by Step
This function is defined at every real number c and f(c)=$5c^{4}-3c+7$.
Also, $\lim\limits_{x \to c}f(x)=\lim\limits_{x \to c}(5x^{4}-3x+7)$
= $5c^{4}-3c+7$
Thus $\lim\limits_{x \to c}f(x)=f(c)$ and hence f is continuous at every real number.
