FOIL

(8x^8-9)(x^9-5)

(8x^8-9)(x^9-5) =

8x^8*x*9 + 8x^8*(-5) -9*x^9 -9*(-5) =
8x^17 - 40x^8 - 9x^9 + 45,
8x^17 - 9x^9 - 40x^8 + 45.