ANSWER
One other root of this polynomial is
[tex]2 - i[/tex]
EXPLANATION
One property of the complex root of a polynomial is the conjugate root property.
If one root of a polynomial is
[tex]a + bi[/tex]
then the conjugate is also a root of this polynomial.
The conjugate of
[tex]a + bi[/tex]
is
[tex]a - bi[/tex]
Also the conjugate of
[tex]a - bi[/tex]
is
[tex]a + bi[/tex]
Therefore if
[tex]2 - i[/tex]
is a root of the polynomial, then its complex conjugate
[tex]2 + i[/tex]
is also a root of that polynomial.
The same applies to purely imaginary complex roots too.
Thus, if
[tex]bi[/tex]
is a root then its conjugate
[tex] - bi[/tex]
is also a root.
