Divide using synthetic division $$ ( x^{3}-2x^{2}+x+18 ) \div ( x+2 ) $$
Answer
The synthetic division table is:
$$ \begin{array}{c|rrrr}-2&1&-2&1&18\\& & -2& 8& \color{black}{-18} \\ \hline &\color{blue}{1}&\color{blue}{-4}&\color{blue}{9}&\color{orangered}{0} \end{array} $$The solution is:
$$ \frac{ x^{3}-2x^{2}+x+18 }{ x+2 } = \color{blue}{x^{2}-4x+9} $$Explanation
Step 1 : Write down the coefficients of the dividend into division table. Put the zero from $ x + 2 = 0 $ ( $ x = \color{blue}{ -2 } $ ) at the left.
$$ \begin{array}{c|rrrr}\color{blue}{-2}&1&-2&1&18\\& & & & \\ \hline &&&& \end{array} $$Step 1 : Bring down the leading coefficient to the bottom row.
$$ \begin{array}{c|rrrr}-2&\color{orangered}{ 1 }&-2&1&18\\& & & & \\ \hline &\color{orangered}{1}&&& \end{array} $$Step 2 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -2 } \cdot \color{blue}{ 1 } = \color{blue}{ -2 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-2}&1&-2&1&18\\& & \color{blue}{-2} & & \\ \hline &\color{blue}{1}&&& \end{array} $$Step 3 : Add down last column: $ \color{orangered}{ -2 } + \color{orangered}{ \left( -2 \right) } = \color{orangered}{ -4 } $
$$ \begin{array}{c|rrrr}-2&1&\color{orangered}{ -2 }&1&18\\& & \color{orangered}{-2} & & \\ \hline &1&\color{orangered}{-4}&& \end{array} $$Step 4 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -2 } \cdot \color{blue}{ \left( -4 \right) } = \color{blue}{ 8 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-2}&1&-2&1&18\\& & -2& \color{blue}{8} & \\ \hline &1&\color{blue}{-4}&& \end{array} $$Step 5 : Add down last column: $ \color{orangered}{ 1 } + \color{orangered}{ 8 } = \color{orangered}{ 9 } $
$$ \begin{array}{c|rrrr}-2&1&-2&\color{orangered}{ 1 }&18\\& & -2& \color{orangered}{8} & \\ \hline &1&-4&\color{orangered}{9}& \end{array} $$Step 6 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -2 } \cdot \color{blue}{ 9 } = \color{blue}{ -18 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-2}&1&-2&1&18\\& & -2& 8& \color{blue}{-18} \\ \hline &1&-4&\color{blue}{9}& \end{array} $$Step 7 : Add down last column: $ \color{orangered}{ 18 } + \color{orangered}{ \left( -18 \right) } = \color{orangered}{ 0 } $
$$ \begin{array}{c|rrrr}-2&1&-2&1&\color{orangered}{ 18 }\\& & -2& 8& \color{orangered}{-18} \\ \hline &\color{blue}{1}&\color{blue}{-4}&\color{blue}{9}&\color{orangered}{0} \end{array} $$Bottom line represents the quotient $ \color{blue}{ x^{2}-4x+9 } $ with a remainder of $ \color{red}{ 0 } $.