combine like terms

18x^4+2x^3y^3-1-2y^3-17x^4=

18x^4+2x^3(y^3)-1-2y^3-17x^4=

x^4 + 2x^3 (y^3) - 2y^3 - 1 =

x^4 + 2x^3 (y^3) - 2y^3 - 1 =

x^4 + 2y^3 (x^3 - 1) - 1

This should be it, unless the parentheses are differently arranged.

I hope this helps. Thanks for asking.