Divide using synthetic division $$ ( x^{4}-5x^{2}+4x+12 ) \div ( x+4 ) $$
Answer
The synthetic division table is:
$$ \begin{array}{c|rrrrr}-4&1&0&-5&4&12\\& & -4& 16& -44& \color{black}{160} \\ \hline &\color{blue}{1}&\color{blue}{-4}&\color{blue}{11}&\color{blue}{-40}&\color{orangered}{172} \end{array} $$The solution is:
$$ \frac{ x^{4}-5x^{2}+4x+12 }{ x+4 } = \color{blue}{x^{3}-4x^{2}+11x-40} ~+~ \frac{ \color{red}{ 172 } }{ x+4 } $$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.
$$ \begin{array}{c|rrrrr}\color{blue}{-4}&1&0&-5&4&12\\& & & & & \\ \hline &&&&& \end{array} $$Step 1 : Bring down the leading coefficient to the bottom row.
$$ \begin{array}{c|rrrrr}-4&\color{orangered}{ 1 }&0&-5&4&12\\& & & & & \\ \hline &\color{orangered}{1}&&&& \end{array} $$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 } $.
$$ \begin{array}{c|rrrrr}\color{blue}{-4}&1&0&-5&4&12\\& & \color{blue}{-4} & & & \\ \hline &\color{blue}{1}&&&& \end{array} $$Step 3 : Add down last column: $ \color{orangered}{ 0 } + \color{orangered}{ \left( -4 \right) } = \color{orangered}{ -4 } $
$$ \begin{array}{c|rrrrr}-4&1&\color{orangered}{ 0 }&-5&4&12\\& & \color{orangered}{-4} & & & \\ \hline &1&\color{orangered}{-4}&&& \end{array} $$Step 4 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -4 } \cdot \color{blue}{ \left( -4 \right) } = \color{blue}{ 16 } $.
$$ \begin{array}{c|rrrrr}\color{blue}{-4}&1&0&-5&4&12\\& & -4& \color{blue}{16} & & \\ \hline &1&\color{blue}{-4}&&& \end{array} $$Step 5 : Add down last column: $ \color{orangered}{ -5 } + \color{orangered}{ 16 } = \color{orangered}{ 11 } $
$$ \begin{array}{c|rrrrr}-4&1&0&\color{orangered}{ -5 }&4&12\\& & -4& \color{orangered}{16} & & \\ \hline &1&-4&\color{orangered}{11}&& \end{array} $$Step 6 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -4 } \cdot \color{blue}{ 11 } = \color{blue}{ -44 } $.
$$ \begin{array}{c|rrrrr}\color{blue}{-4}&1&0&-5&4&12\\& & -4& 16& \color{blue}{-44} & \\ \hline &1&-4&\color{blue}{11}&& \end{array} $$Step 7 : Add down last column: $ \color{orangered}{ 4 } + \color{orangered}{ \left( -44 \right) } = \color{orangered}{ -40 } $
$$ \begin{array}{c|rrrrr}-4&1&0&-5&\color{orangered}{ 4 }&12\\& & -4& 16& \color{orangered}{-44} & \\ \hline &1&-4&11&\color{orangered}{-40}& \end{array} $$Step 8 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -4 } \cdot \color{blue}{ \left( -40 \right) } = \color{blue}{ 160 } $.
$$ \begin{array}{c|rrrrr}\color{blue}{-4}&1&0&-5&4&12\\& & -4& 16& -44& \color{blue}{160} \\ \hline &1&-4&11&\color{blue}{-40}& \end{array} $$Step 9 : Add down last column: $ \color{orangered}{ 12 } + \color{orangered}{ 160 } = \color{orangered}{ 172 } $
$$ \begin{array}{c|rrrrr}-4&1&0&-5&4&\color{orangered}{ 12 }\\& & -4& 16& -44& \color{orangered}{160} \\ \hline &\color{blue}{1}&\color{blue}{-4}&\color{blue}{11}&\color{blue}{-40}&\color{orangered}{172} \end{array} $$Bottom line represents the quotient $ \color{blue}{ x^{3}-4x^{2}+11x-40 } $ with a remainder of $ \color{red}{ 172 } $.