## Precalculus (6th Edition) Blitzer

$2x^3-x^6$
Starting with the given expression: $x^3+x^3-x^3\cdot x^3$. Multiply the last two terms, we have: $x^3+x^3-x^6$ Combine the like terms, we have: $2x^3-x^6$. Since this term can no longer be simplified, therefore this is our answer.