let p(x) = x^3-ax, where a is constant

a.) if a<0, show that p(x) is alwayss increasing

b.) if a>0, show that p(x) has a local maximum and minimum

c.) sketch and label typical graphs for the cases when a<0 and when a>0

can i get some help with this one please, i just dont know what to do...thanks

mathlete