Perhaps I haven't had enough coffee... is there a bug in the graph app relative to (for example) x^3/(x+1)? I don't see why there should be that parabolic looking bit in Q II.

Jan 26, 2016

No, the graph utility is working just fine.

Explanation:

I have a feeling that this is more of a math problem than an actual bug.

Try plotting that function on any other online graph calculator, you'll get the exact same curve.

For example, let's say that $x = 3$. This will get you

$y = {3}^{3} / \left(3 + 1\right) = \frac{27}{4}$

But for

$y = \frac{27}{4} = {x}^{3} / \left(x + 1\right)$

you also get

$4 {x}^{3} - 27 x - 27 = 0$

This will produce

$\left\{\left({x}_{1} = 3\right) , \left({x}_{2 , 3} = - 1.5\right)\right.$

The vertex of that parabolic thing lies at $\left(- \frac{3}{2} , \frac{27}{4}\right)$, so I guess that makes sense after all.