Hi there

I have a start on this polynomial:

$\displaystyle f(z) = x^4 - 2z^2 - 16z - 15$

If I let f(z) = f(-1) I will find that the expression equals zero and so (z+1) is a factor.

But where do I go from here?

The answer in the back of the book is (z+1)(z+1+2i)(z+1-2i)(z-3)

cheers

David.