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