Step 1 :The end behavior of a function is determined by the leading term, which is the term with the highest degree. In this case, the leading term is -3x^4.
Step 2 :As x approaches negative or positive infinity, the value of the function will be dominated by this term.
Step 3 :Since the degree of the leading term is even and the coefficient is negative, as x approaches negative infinity, the function will approach positive infinity, and as x approaches positive infinity, the function will approach negative infinity.
Step 4 :\(\boxed{\text{As } x \rightarrow -\infty, f(x) \rightarrow \infty}\)
Step 5 :\(\boxed{\text{As } x \rightarrow \infty, f(x) \rightarrow -\infty}\)