Complex Numbers!

[NeedHelpWithStudy]

Hey guys, well i need help with the following question:
Extended response Q7):
(a) Find the square roots of z= -2 - 2root3i, giving the answers in cartesian form.
(b) Find the square roots of z= 2 + 2root3, giving the answers in cartesian form.
(c) Show that if w is a square root of z , then iw is a square root of -z.
Well i was able to do part (a), and par (b) since it has a -z i thought i should cancel it out and find the answer, when i cancelled the - out i got the part b equation to be as same as part a, then i got the same answer for part (b) as part (a). When i checked the answer at the back of the book it told me it was wrong. part(a)'s answer was correct and it was +/- (1-root3i), and for part (b) the answer was +/- (root3 + i). But when i tried to do part (b) without cancelling out the negative i was able to obtain the correct answer, can someone explain why i shouldn't cancel out the - part of the z? and if you could, can you please do this question and show me how it is done if possible. Not sure how to do part c at this stage. Thanks in advance.

[kinslayer]

Well i was able to do part (a), and par (b) since it has a -z i thought i should cancel it out and find the answer

I am not sure what you mean here. I don't see any -z in part (b). And actually in part (b) you have z equal to a real number.. I assume the equation is supposed to be ?

Showing part (c) is simple. If , then

edit: I see what you mean with the -z. Part (b) is just asking you to find the square root of -z, where the z is from part (a). To do that, just use part (c) -- multiply by i: