Divide using synthetic division $$ ( x^{3}-8x+6 ) \div ( x+8 ) $$
Answer
The synthetic division table is:
$$ \begin{array}{c|rrrr}-8&1&0&-8&6\\& & -8& 64& \color{black}{-448} \\ \hline &\color{blue}{1}&\color{blue}{-8}&\color{blue}{56}&\color{orangered}{-442} \end{array} $$The solution is:
$$ \frac{ x^{3}-8x+6 }{ x+8 } = \color{blue}{x^{2}-8x+56} \color{red}{~-~} \frac{ \color{red}{ 442 } }{ x+8 } $$Explanation
Step 1 : Write down the coefficients of the dividend into division table. Put the zero from $ x + 8 = 0 $ ( $ x = \color{blue}{ -8 } $ ) at the left.
$$ \begin{array}{c|rrrr}\color{blue}{-8}&1&0&-8&6\\& & & & \\ \hline &&&& \end{array} $$Step 1 : Bring down the leading coefficient to the bottom row.
$$ \begin{array}{c|rrrr}-8&\color{orangered}{ 1 }&0&-8&6\\& & & & \\ \hline &\color{orangered}{1}&&& \end{array} $$Step 2 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -8 } \cdot \color{blue}{ 1 } = \color{blue}{ -8 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-8}&1&0&-8&6\\& & \color{blue}{-8} & & \\ \hline &\color{blue}{1}&&& \end{array} $$Step 3 : Add down last column: $ \color{orangered}{ 0 } + \color{orangered}{ \left( -8 \right) } = \color{orangered}{ -8 } $
$$ \begin{array}{c|rrrr}-8&1&\color{orangered}{ 0 }&-8&6\\& & \color{orangered}{-8} & & \\ \hline &1&\color{orangered}{-8}&& \end{array} $$Step 4 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -8 } \cdot \color{blue}{ \left( -8 \right) } = \color{blue}{ 64 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-8}&1&0&-8&6\\& & -8& \color{blue}{64} & \\ \hline &1&\color{blue}{-8}&& \end{array} $$Step 5 : Add down last column: $ \color{orangered}{ -8 } + \color{orangered}{ 64 } = \color{orangered}{ 56 } $
$$ \begin{array}{c|rrrr}-8&1&0&\color{orangered}{ -8 }&6\\& & -8& \color{orangered}{64} & \\ \hline &1&-8&\color{orangered}{56}& \end{array} $$Step 6 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -8 } \cdot \color{blue}{ 56 } = \color{blue}{ -448 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-8}&1&0&-8&6\\& & -8& 64& \color{blue}{-448} \\ \hline &1&-8&\color{blue}{56}& \end{array} $$Step 7 : Add down last column: $ \color{orangered}{ 6 } + \color{orangered}{ \left( -448 \right) } = \color{orangered}{ -442 } $
$$ \begin{array}{c|rrrr}-8&1&0&-8&\color{orangered}{ 6 }\\& & -8& 64& \color{orangered}{-448} \\ \hline &\color{blue}{1}&\color{blue}{-8}&\color{blue}{56}&\color{orangered}{-442} \end{array} $$Bottom line represents the quotient $ \color{blue}{ x^{2}-8x+56 } $ with a remainder of $ \color{red}{ -442 } $.