I have a problem that i am completely stuck on, stuck to the point that i don't even know how to approach it. If someone could simply get me started i can do the rest. Any help is appreciated, thanks.

Problem: The area of the region bounded by the graphs of y=x^3 and y=x cannot be found by the single integral ∫(ranging from -1 to 1) [X^3-X]Dx. Explain why this is so. Use symmetry to write a single integral that does represent the area.