Is this a cubic function?

Question

darkbluechocobo · Answer

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tkhunny · Answer

Tough call.  That $might$ be a cubic.  Could be Quintic, I suppose.  It may also be an inverse trigonometric function.

If I HAD to, I would say cubic, but I'm pretty nervous about it.

anonymous · Answer

no it is not

darkbluechocobo · Answer

Well I looked at what a quintic function is and it looks like this so i think i should put neither

tkhunny · Answer

Well, "neither" doesn't make any sense.  The word "neither" applies to things with only 2 choices.  Since you have 3 other choices, "neither" doesn't mean anything.

Like I said, it COULD BE a cubic.  I'm not sure where 893225 has gained such confidence.

anonymous · Answer

That graph looks weird. If it was a cubic (the lines are spaced by 1s since after 5 lines I hit 5 in any direction) then the y value corresponding to 5 would have an x-coordinate of 1.70998 (the cbrt of 5 just working backwards).  But that's all the way over by the 3s,

tkhunny · Answer

I agree that some eyeball characteristics can be observed.  There just isn't enough information to be that sure.

tkhunny · Answer

Try out $y = 0.2x^{3}-0.15x^{2}+0.15x$.  This is definitely cubic and it comes very close to the given graph.

I can easily create a quintic that does the same thing.

Just an example of how we can talk ourselves into things.

The right answer is that it MAY be cubic.  There just isn't enough inforamation.