18x^4+2x^3y^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.
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