what does it mean when f'(x)=0?

what are the intervals where f'(x)>o and f'(x)<0?

what does it imply when and or the other way around?

maybe, i can't wait for your reply.. anyways, these are the interpretations..

if , then surely, f has a rel min or max at

suppose, and , then f assumes a rel min at ; for the other case, f assumes a relative max.. Ü