We can multiply polynomials by using a GRID METHOD
Write one of the polynomials across the top and the other down the left side.
$$ \begin{darray}{|c|c|c|c|}\hline & \color{blue}{x^2} & \color{blue}{x} & \color{blue}{-2} \\ \hline \color{blue}{x^2} & & & \\ \hline \color{blue}{-x} & & & \\ \hline \color{blue}{-6} & & & \\ \hline \end{darray} $$Fill in each empty box by multiplying the intersecting terms.
$$ \begin{darray}{|c|c|c|c|}\hline & \color{blue}{x^2} & \color{blue}{x} & \color{blue}{-2} \\ \hline \color{blue}{x^2} & \color{orangered}{x^4} & \color{orangered}{x^3} & \color{orangered}{-2x^2} \\ \hline \color{blue}{-x} & \color{orangered}{-x^3} & \color{orangered}{-x^2} & \color{orangered}{2x} \\ \hline \color{blue}{-6} & \color{orangered}{-6x^2} & \color{orangered}{-6x} & \color{orangered}{12} \\ \hline \end{darray} $$Combine like terms:
$$ x^4 + x^3-x^3-2x^2-x^2-6x^2 + 2x-6x + 12 = \\ x^4-9x^2-4x+12 $$