Graphically, the local maximum can be localized by spotting the "highest value" inside a range. A local maximum point on a function is a point (x,y) on the graph of the function whose y coordinate is larger than all other y coordinates on the graph at points "close to'' (x,y).
We can see that in our g function at x= -2 and x = 3, with respective values y = 3 and y = -1.
The answer for item (a) is: -1, 3
For item (b): -2, 3