During the first stage of the division process you should have subtracted $\displaystyle{{x}}^{{3}}+{4}{{x}}^{{2}}+{6}{x}\usepackage{cmbright}\Huge\$ from the dividend. While subtracting $\displaystyle{{x}}^{{3}}\usepackage{cmbright}\Huge\$ and $\displaystyle{6}{x}\usepackage{cmbright}\Huge\$ , you may have added $\displaystyle{4}{{x}}^{{2}}\usepackage{cmbright}\Huge\$ to the dividend. Make sure that you distribute the minus sign when you get to the steps involving subtraction.