Let y=r(x) be continuous and differentiable. Assume r'(x)=0 r′(x)=0 at x=ax=a.
If r'(x)<0 before x=a and r'(x)>0 after x=a

what must be true about r(a)?r(a)?
Choice 1: r(a) is a maximum value
Choice 2: r(a) is a minimum value
Choice 3: cannot determine based on this information