Polynomial functions

(1) One zero is 2 - i, the other zero is 2 + i
(x - 2 + i)(x - 2 - i) = (x - 2)^2 + 1 = x^2 - 4x + 5
Using long division, (x^3 - 7x^2 + 17x - 15)/(x^2 - 4x + 5) = (x - 3)
The 3 zero's are 3, 2 + i and 2 - i
(2) One zero is i, another zero is -i
(x - i)(x + i) = x^2 + 1
Using long division (x^4+10x^3+27x^2+10x+26)/(x^2 + 1) = x^2 + 10x + 26
x^2 + 10x + 26 = 0 => x = [-10 +/- √(100 - 104)]/2 = -5 +/- i
The 4 zero's are i, -i, -5 + i and -5 - i