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