Hi, I'm stuck on this one. I don't know why though. The answer in the book is 8.

if and , then a is equal to?

A) 4 B) -6 C) 8 D) 6 E) 5

So the first thing I saw was that there is a conjugate zero also so it looks like this

So then I thought i would expand out just the z's, not the z^2s etc. and let them equal the z term in the original expression, -6z

the z cancels out

So then I now have (z - 1 - i)(z - 1 + i)(z - 1) and I will just expand our the constants to get the a

But this doesn't seem to work. I won't bother writing it down because I have done it about 5 times and I can't seem to get the answer. Does anyone know a method to get this one out?

David.