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