Incorrect. Remember that you should distribute the negative sign to each term in the second set of parentheses. Here is another way to write this problem: $\displaystyle{8}{{x}}^{{3}}-{2}{{x}}^{{3}}-{4}{{x}}^{{2}}-{9}{{x}}^{{2}}+{x}-{4}{x}\usepackage{cmbright}\Huge\$ . Does this make it easier for you to simplify the expression?