Divide using synthetic division $$ ( x^{3}-5x^{2}+4x+6 ) \div ( x+4 ) $$
Answer
The synthetic division table is:
$$ \begin{array}{c|rrrr}-4&1&-5&4&6\\& & -4& 36& \color{black}{-160} \\ \hline &\color{blue}{1}&\color{blue}{-9}&\color{blue}{40}&\color{orangered}{-154} \end{array} $$The solution is:
$$ \frac{ x^{3}-5x^{2}+4x+6 }{ x+4 } = \color{blue}{x^{2}-9x+40} \color{red}{~-~} \frac{ \color{red}{ 154 } }{ x+4 } $$Explanation
Step 1 : Write down the coefficients of the dividend into division table. Put the zero from $ x + 4 = 0 $ ( $ x = \color{blue}{ -4 } $ ) at the left.
$$ \begin{array}{c|rrrr}\color{blue}{-4}&1&-5&4&6\\& & & & \\ \hline &&&& \end{array} $$Step 1 : Bring down the leading coefficient to the bottom row.
$$ \begin{array}{c|rrrr}-4&\color{orangered}{ 1 }&-5&4&6\\& & & & \\ \hline &\color{orangered}{1}&&& \end{array} $$Step 2 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -4 } \cdot \color{blue}{ 1 } = \color{blue}{ -4 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-4}&1&-5&4&6\\& & \color{blue}{-4} & & \\ \hline &\color{blue}{1}&&& \end{array} $$Step 3 : Add down last column: $ \color{orangered}{ -5 } + \color{orangered}{ \left( -4 \right) } = \color{orangered}{ -9 } $
$$ \begin{array}{c|rrrr}-4&1&\color{orangered}{ -5 }&4&6\\& & \color{orangered}{-4} & & \\ \hline &1&\color{orangered}{-9}&& \end{array} $$Step 4 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -4 } \cdot \color{blue}{ \left( -9 \right) } = \color{blue}{ 36 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-4}&1&-5&4&6\\& & -4& \color{blue}{36} & \\ \hline &1&\color{blue}{-9}&& \end{array} $$Step 5 : Add down last column: $ \color{orangered}{ 4 } + \color{orangered}{ 36 } = \color{orangered}{ 40 } $
$$ \begin{array}{c|rrrr}-4&1&-5&\color{orangered}{ 4 }&6\\& & -4& \color{orangered}{36} & \\ \hline &1&-9&\color{orangered}{40}& \end{array} $$Step 6 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -4 } \cdot \color{blue}{ 40 } = \color{blue}{ -160 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-4}&1&-5&4&6\\& & -4& 36& \color{blue}{-160} \\ \hline &1&-9&\color{blue}{40}& \end{array} $$Step 7 : Add down last column: $ \color{orangered}{ 6 } + \color{orangered}{ \left( -160 \right) } = \color{orangered}{ -154 } $
$$ \begin{array}{c|rrrr}-4&1&-5&4&\color{orangered}{ 6 }\\& & -4& 36& \color{orangered}{-160} \\ \hline &\color{blue}{1}&\color{blue}{-9}&\color{blue}{40}&\color{orangered}{-154} \end{array} $$Bottom line represents the quotient $ \color{blue}{ x^{2}-9x+40 } $ with a remainder of $ \color{red}{ -154 } $.