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