We must identify which graph corresponds to the function:
[tex]f(x)=x^3+2x^2-4x-1.[/tex]
1) The function f(x) is a polynomial of degree 3, so it has 3 roots, i.e. it must cross the x-axis in 3 places. Taking into account this fact, we know that the 1st and 3rd graphs cannot represent the function f(x).
2) Now, when x takes a very big value, the cubic term of the polynomial dominates, and f(x) > 0 for x → ∞. From the remaining options, we see that the 2nd takes f(x) < 0 for x → ∞, so we can discard that option. The remaining option is the 4th graph, so we conclude that that is the correct option.
Answer: 4th graph.
