The given polynomial is of the form \( \left( x + \sqrt{x^4 - 1} \right)^9 + \left( x - \sqrt{x^4 - 1} \right)^9 \). The degree of each term is determined by the highest power of \( x \) in the expansion of each binomial. Since we are dealing with terms of degree 9 in the expansions of both polynomials, the degree of the resulting polynomial is \( 17 \) after combining terms.