Divide using synthetic division $$ ( x^{4}+2x^{3}-7x^{2}-14 ) \div ( x+2 ) $$
Answer
The synthetic division table is:
$$ \begin{array}{c|rrrrr}-2&1&2&-7&0&-14\\& & -2& 0& 14& \color{black}{-28} \\ \hline &\color{blue}{1}&\color{blue}{0}&\color{blue}{-7}&\color{blue}{14}&\color{orangered}{-42} \end{array} $$The solution is:
$$ \frac{ x^{4}+2x^{3}-7x^{2}-14 }{ x+2 } = \color{blue}{x^{3}-7x+14} \color{red}{~-~} \frac{ \color{red}{ 42 } }{ x+2 } $$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.
$$ \begin{array}{c|rrrrr}\color{blue}{-2}&1&2&-7&0&-14\\& & & & & \\ \hline &&&&& \end{array} $$Step 1 : Bring down the leading coefficient to the bottom row.
$$ \begin{array}{c|rrrrr}-2&\color{orangered}{ 1 }&2&-7&0&-14\\& & & & & \\ \hline &\color{orangered}{1}&&&& \end{array} $$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 } $.
$$ \begin{array}{c|rrrrr}\color{blue}{-2}&1&2&-7&0&-14\\& & \color{blue}{-2} & & & \\ \hline &\color{blue}{1}&&&& \end{array} $$Step 3 : Add down last column: $ \color{orangered}{ 2 } + \color{orangered}{ \left( -2 \right) } = \color{orangered}{ 0 } $
$$ \begin{array}{c|rrrrr}-2&1&\color{orangered}{ 2 }&-7&0&-14\\& & \color{orangered}{-2} & & & \\ \hline &1&\color{orangered}{0}&&& \end{array} $$Step 4 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -2 } \cdot \color{blue}{ 0 } = \color{blue}{ 0 } $.
$$ \begin{array}{c|rrrrr}\color{blue}{-2}&1&2&-7&0&-14\\& & -2& \color{blue}{0} & & \\ \hline &1&\color{blue}{0}&&& \end{array} $$Step 5 : Add down last column: $ \color{orangered}{ -7 } + \color{orangered}{ 0 } = \color{orangered}{ -7 } $
$$ \begin{array}{c|rrrrr}-2&1&2&\color{orangered}{ -7 }&0&-14\\& & -2& \color{orangered}{0} & & \\ \hline &1&0&\color{orangered}{-7}&& \end{array} $$Step 6 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -2 } \cdot \color{blue}{ \left( -7 \right) } = \color{blue}{ 14 } $.
$$ \begin{array}{c|rrrrr}\color{blue}{-2}&1&2&-7&0&-14\\& & -2& 0& \color{blue}{14} & \\ \hline &1&0&\color{blue}{-7}&& \end{array} $$Step 7 : Add down last column: $ \color{orangered}{ 0 } + \color{orangered}{ 14 } = \color{orangered}{ 14 } $
$$ \begin{array}{c|rrrrr}-2&1&2&-7&\color{orangered}{ 0 }&-14\\& & -2& 0& \color{orangered}{14} & \\ \hline &1&0&-7&\color{orangered}{14}& \end{array} $$Step 8 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -2 } \cdot \color{blue}{ 14 } = \color{blue}{ -28 } $.
$$ \begin{array}{c|rrrrr}\color{blue}{-2}&1&2&-7&0&-14\\& & -2& 0& 14& \color{blue}{-28} \\ \hline &1&0&-7&\color{blue}{14}& \end{array} $$Step 9 : Add down last column: $ \color{orangered}{ -14 } + \color{orangered}{ \left( -28 \right) } = \color{orangered}{ -42 } $
$$ \begin{array}{c|rrrrr}-2&1&2&-7&0&\color{orangered}{ -14 }\\& & -2& 0& 14& \color{orangered}{-28} \\ \hline &\color{blue}{1}&\color{blue}{0}&\color{blue}{-7}&\color{blue}{14}&\color{orangered}{-42} \end{array} $$Bottom line represents the quotient $ \color{blue}{ x^{3}-7x+14 } $ with a remainder of $ \color{red}{ -42 } $.