hi

have function

has derivative

i factor out 1/3 and ignored as it always positive and got then set it to zero and got x= and used these to get coordinates, which i am happy with but when i try to find the max and min locals of g(x) i get the oposite result to the graph of g(x). no matter how i try to look at it i get , as minimum point and , as a maximum point. have been using first derivitive test as i am unable to work out how to get g''(x)

any help would be great