We can multiply polynomials by using a GRID METHOD
Write one of the polynomials across the top and the other down the left side.
$$ \begin{darray}{|c|c|c|c|}\hline & \color{blue}{4p^2} & \color{blue}{p} & \color{blue}{3} \\ \hline \color{blue}{p} & & & \\ \hline \color{blue}{-3} & & & \\ \hline \end{darray} $$Fill in each empty box by multiplying the intersecting terms.
$$ \begin{darray}{|c|c|c|c|}\hline & \color{blue}{4p^2} & \color{blue}{p} & \color{blue}{3} \\ \hline \color{blue}{p} & \color{orangered}{4p^3} & \color{orangered}{p^2} & \color{orangered}{3p} \\ \hline \color{blue}{-3} & \color{orangered}{-12p^2} & \color{orangered}{-3p} & \color{orangered}{-9} \\ \hline \end{darray} $$Combine like terms:
$$ 4p^3 + p^2-12p^2 + 3p-3p-9 = \\ 4p^3-11p^2-9 $$