Concept

Absolute Minimum and Maximum

The absolute minimum, or global minimum, of a function is the least output in its whole domain.
Absolute minimum of a quartic function 0.3*(x+3)*(x+2)*(x+1)*(x-1) located at (0.326345,-2.07423)

The absolute maximum, or global maximum, of a function is defined in a similar way. It is the greatest output of the function in its whole domain.

Absolute minimum of a quartic function -0.3*(x+2.5)*(x+1)*(x)*(x-2) located at (1.3,2.38602)
The absolute maximum of a function is also a relative maximum, and the absolute minimum is also a relative minimum. If a function increases indefinitely, it does not have an absolute maximum. Likewise, if a function decreases indefinitely, it does not have an absolute minimum. The function might still have relative extrema.
Different functions with different extrema
Exercises