Hey I really need some help with some questions!:

a) Express

http://img23.imageshack.us/img23/7374/mathss.jpg

in exponential form

- I got 8e^(-3pi/4) is this correct?

b) Find three cube roots of

http://img23.imageshack.us/img23/7374/mathss.jpg

, giving answers in simplified exponential form

- I have no idea how to do this, please help?

c) Then approximate the answers in Cartesian form, a + bi, where a and b are given to two decimal placesthanks guys