Question 404705
  <pre><font size = 3 color = "indigo"><b>
Hi
solving:
Z^4+8z^3-9z^2=0
z^2(z^2 + 8z - 9)= 0
z^2= 0   z= 0
(z^2 + 8z - 9)= 0
factoring
(z+9)(z-1)= 0 Note:SUM of the inner product(9z) and the outer product(-z) = 8z
(z+9)=0   z = -9
(z-1)= 0  z = 1