I have the following function:

$\displaystyle f(x)=6x^2-x-2$

I've worked out the derivative of this function:

$\displaystyle f'(x)=12x-1$

I've also worked out the minimum:

$\displaystyle (\frac{1}{12}, \frac{-49}{24})$

However, I am unsure how I can prove/show that there is no maximum to this function?