Multiply polynomial $ \, \color{blue}{ x+2 } \, $ by $ \, \color{orangered}{ x^3+x^2-1 }$.

$$ \left( \color{blue}{x+2} \right) \cdot \left( \color{orangered}{x^3+x^2-1} \right) = x^4+3x^3+2x^2-x-2 $$

We can multiply polynomials by using a GRID METHOD

Write one of the polynomials across the top and the other down the left side.

$$ \begin{darray}{|c|c|c|c|}\hline & \color{blue}{x^3} & \color{blue}{x^2} & \color{blue}{-1} \\ \hline \color{blue}{x} & & & \\ \hline \color{blue}{2} & & & \\ \hline \end{darray} $$

Fill in each empty box by multiplying the intersecting terms.

$$ \begin{darray}{|c|c|c|c|}\hline & \color{blue}{x^3} & \color{blue}{x^2} & \color{blue}{-1} \\ \hline \color{blue}{x} & \color{orangered}{x^4} & \color{orangered}{x^3} & \color{orangered}{-x} \\ \hline \color{blue}{2} & \color{orangered}{2x^3} & \color{orangered}{2x^2} & \color{orangered}{-2} \\ \hline \end{darray} $$

Combine like terms:

$$ x^4 + x^3 + 2x^3-x + 2x^2-2 = \\ x^4+3x^3+2x^2-x-2 $$

Polynomial Operations Calculator