Consider the function .
This function has an absolute minimum value equal to
and an absolute maximum value equal to
Absolute max or min is where first derivative is zero.
So absolute max or min can be at or . But to find out which one which you plug-in the values into the function and find out which one's larger than the other.
Now plug-in and separately into you'll find that
The function has absolute max at
And has absolute min at
You can check it in the following graph to be sure: