TeX source:
\begin{array}{rclcl} 485 &=& 7x^6-4x^3+5 & \vert & -485 \cr 0 &=& 7x^6-4x^3-480 & \vert & :7 \cr 0 &=& x^6-\dfrac{4}{7}x^3-\dfrac{480}{7} \cr 0 &=& \left(x^3\right)^2-\dfrac{4}{7}x^3-\dfrac{480}{7} \end{array}