Imaginary numbers/complex numbers

Hi there,

Could somebody help me with these questions, explaining the solutions and maybe providing some good references for learning?

1)i) Simplify

$\displaystyle i^7, i^-3, i^9$

ii) Find

$\displaystyle (3 + 5i) + (7 - i)$

iii) Find

$\displaystyle 2 / 1 - i$

2)i) Evaluate

$\displaystyle (2 + 3i) + (2 - 3i)$

ii)

$\displaystyle 7 - 3i/2 + 4i$

iii)

$\displaystyle i^5(1 + i^5)$

I'd be very appreciative with some help in understanding/solving these types of question.

Regards,