2=0 is a contradiction, so we have no inflection points on this function, so ¿How could I determine the concavity if I have no inflection points?
Should I take the "0" as a refered point, then evaluate the f''(x) (for example) with f''(-1) and f''(1) to determine the concavity?
Because on that case, I can effectively determinate the concavity, but is this legal? ¿why I'd take the "0"? On this case, I've take the "0" just because I've seen the graph previously.