Further Maths Help!

So I'm doing FP2 in January and there's parts of De Moivre's that I didn't really understand from the textbook. Anyone out there care to explain to me:

1. Exponential Form of a Complex Number
2. Cube roots of unity
3. Nth Roots of unity
4. The roots of Z^n=a, where a is a non-real number.

Thank you!

Are you working solely from a textbook or do you have teacher support? Where are you struggling with the explanations in the book?

The starting point is that we can write any complex number in the form $re^{i\theta}$ where $i=\sqrt{-1}$ - everything else follows from that.