I dont know how to determine if these points are local min m

I don\'t know how to determine if these points are local min, max or saddle point just by looking at the graph. Would you like to explain how and why? Thanks!

Solution

Here P is   givinf minimum value y=-6 at x=0

Here Q is on the left side giving   0 at x=-1   saddle point

Here R is the at top giving 2 at x=-2 saddle point

Here S is at top giving   3 at x=0 maximum values