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