We can multiply polynomials by using a GRID METHOD
Write one of the polynomials across the top and the other down the left side.
$$ \begin{darray}{|c|c|c|c|}\hline & \color{blue}{6a^2} & \color{blue}{-a} & \color{blue}{2} \\ \hline \color{blue}{4a} & & & \\ \hline \color{blue}{2} & & & \\ \hline \end{darray} $$Fill in each empty box by multiplying the intersecting terms.
$$ \begin{darray}{|c|c|c|c|}\hline & \color{blue}{6a^2} & \color{blue}{-a} & \color{blue}{2} \\ \hline \color{blue}{4a} & \color{orangered}{24a^3} & \color{orangered}{-4a^2} & \color{orangered}{8a} \\ \hline \color{blue}{2} & \color{orangered}{12a^2} & \color{orangered}{-2a} & \color{orangered}{4} \\ \hline \end{darray} $$Combine like terms:
$$ 24a^3-4a^2 + 12a^2 + 8a-2a + 4 = \\ 24a^3+8a^2+6a+4 $$