Question
Multiply polynomial $ \, \color{blue}{ x^2-7x-18 } \, $ by $ \, \color{orangered}{ x+1 }$.
Answer
$$ \left( \color{blue}{x^2-7x-18} \right) \cdot \left( \color{orangered}{x+1} \right) = x^3-6x^2-25x-18 $$
Explanation
We can multiply polynomials by using a GRID METHOD
Write one of the polynomials across the top and the other down the left side.
$$ \begin{darray}{|c|c|c|c|}\hline & \color{blue}{x^2} & \color{blue}{-7x} & \color{blue}{-18} \\ \hline \color{blue}{x} & & & \\ \hline \color{blue}{1} & & & \\ \hline \end{darray} $$Fill in each empty box by multiplying the intersecting terms.
$$ \begin{darray}{|c|c|c|c|}\hline & \color{blue}{x^2} & \color{blue}{-7x} & \color{blue}{-18} \\ \hline \color{blue}{x} & \color{orangered}{x^3} & \color{orangered}{-7x^2} & \color{orangered}{-18x} \\ \hline \color{blue}{1} & \color{orangered}{x^2} & \color{orangered}{-7x} & \color{orangered}{-18} \\ \hline \end{darray} $$Combine like terms:
$$ x^3-7x^2 + x^2-18x-7x-18 = \\ x^3-6x^2-25x-18 $$This page was created using
Polynomial Operations Calculator