Originally Posted by

**boblee** thanks, but, correct me if I'm wrong, after looking it over wouldn't it be the following?

$\displaystyle x^4-4x^3+6x^2-4x-5$

$\displaystyle

= x^4+x^2+(-4x^3-4x)+5x^2+5$

$\displaystyle = x^2(x^2+1)-4x(x^2+1)+5(x^2+1)$

from there I get:

$\displaystyle = (x^2-4x+5)(x^2+1)$ ....... **OK**

$\displaystyle x^2+1=0$

$\displaystyle x^2=-1 $

$\displaystyle x=-1^{1/2}$

$\displaystyle x=+/-i $ ....... **OK**

$\displaystyle x^2-4x+5=0$

$\displaystyle x=(4+/-(-4^2-4*1*5)^{1/2})/2$

$\displaystyle = (4+/-(16-20)^{1/2})/2$

$\displaystyle = (4+/-(-4)^{1/2})/2$ ....... **OK**

$\displaystyle = {\color{red}\bold{2}}+/-i $ ... **!!!**

Did I do that right?

Thanks for your help.