this polynomial has a degree of 9.
The degree of a polynomial is the highest power of the unknown with a non-zero coeficient.
This expresion has unknown x raised to the 5th, 4th, 9th and 1st power
(x=x1)
with coeficients of : 1,-3,+3 and -2 respectively. So the highest power (i.e. the degree of the polynomial) is 9.