About the absolute extrema ,
1- find the critical numbers
2- put the interval values
3- use them to solve the equation.
Ex if we had x=1 as a critical number and x=2 and x = 3 and the interval [2,3]
my questions :
1- if all values were positive or negative , is there an absolute extrema ?
2- does it matter if the interval was open or closed in this case ?

Question

About the absolute extrema , 
1- find the critical numbers
2- put the interval values
3- use them to solve the equation.
Ex if we had x=1 as a critical number and x=2 and x = 3 and the interval [2,3]
my questions :
1- if all values were positive or negative  , is there an absolute extrema ? 
2- does it matter if the interval was open or closed in this case ?

loser66 · Answer

1/ 1 is not in the interval, reject that point
2/ if all values were positive or negative, which greatest is maximum, which smallest is minimum
3/ Yes, it does matter if the interval was open or closed. for example if it is closed, 2,3 are candidate value to consider the max/ min. You must conclude f (2) and f(3) to compare
If it is open, you don't have those points when considering the max/ min

anonymous · Answer

thanks man , you helped a lot ^^