A function is symmetric with respect to the $x$-axis if and only if $f(x) = f(-x)$ for all $x$ in the domain of $f$. In this case, we have $f(x) = 3x^4 - 3$. If we replace $x$ with $-x$, we get $f(-x) = 3(-x)^4 - 3 = 3x^4 - 3 = f(x)$. Therefore, the function is
Show more…
