改良版

https://www.wolframalpha.com/input/?i=%286x%5E2-9x%2B369%29%5E2%2B%283x%2B1%29%5E4%2Bx%5E6%2B%28-x%5E2-39%29%5E3&;lang=ja

(6x^2-9x+369)^2+(3x+1)^4+x^6+(-x^2-39)^3
= 76843 - 6630 x

6630 = 2×3×5×13×17 なのでu^7いらない