Divide using synthetic division $$ ( x^{3}+x^{2}+9x ) \div ( x-1 ) $$
Answer
The synthetic division table is:
$$ \begin{array}{c|rrrr}1&1&1&9&0\\& & 1& 2& \color{black}{11} \\ \hline &\color{blue}{1}&\color{blue}{2}&\color{blue}{11}&\color{orangered}{11} \end{array} $$The solution is:
$$ \frac{ x^{3}+x^{2}+9x }{ x-1 } = \color{blue}{x^{2}+2x+11} ~+~ \frac{ \color{red}{ 11 } }{ x-1 } $$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.
$$ \begin{array}{c|rrrr}\color{blue}{1}&1&1&9&0\\& & & & \\ \hline &&&& \end{array} $$Step 1 : Bring down the leading coefficient to the bottom row.
$$ \begin{array}{c|rrrr}1&\color{orangered}{ 1 }&1&9&0\\& & & & \\ \hline &\color{orangered}{1}&&& \end{array} $$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 } $.
$$ \begin{array}{c|rrrr}\color{blue}{1}&1&1&9&0\\& & \color{blue}{1} & & \\ \hline &\color{blue}{1}&&& \end{array} $$Step 3 : Add down last column: $ \color{orangered}{ 1 } + \color{orangered}{ 1 } = \color{orangered}{ 2 } $
$$ \begin{array}{c|rrrr}1&1&\color{orangered}{ 1 }&9&0\\& & \color{orangered}{1} & & \\ \hline &1&\color{orangered}{2}&& \end{array} $$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 } $.
$$ \begin{array}{c|rrrr}\color{blue}{1}&1&1&9&0\\& & 1& \color{blue}{2} & \\ \hline &1&\color{blue}{2}&& \end{array} $$Step 5 : Add down last column: $ \color{orangered}{ 9 } + \color{orangered}{ 2 } = \color{orangered}{ 11 } $
$$ \begin{array}{c|rrrr}1&1&1&\color{orangered}{ 9 }&0\\& & 1& \color{orangered}{2} & \\ \hline &1&2&\color{orangered}{11}& \end{array} $$Step 6 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ 1 } \cdot \color{blue}{ 11 } = \color{blue}{ 11 } $.
$$ \begin{array}{c|rrrr}\color{blue}{1}&1&1&9&0\\& & 1& 2& \color{blue}{11} \\ \hline &1&2&\color{blue}{11}& \end{array} $$Step 7 : Add down last column: $ \color{orangered}{ 0 } + \color{orangered}{ 11 } = \color{orangered}{ 11 } $
$$ \begin{array}{c|rrrr}1&1&1&9&\color{orangered}{ 0 }\\& & 1& 2& \color{orangered}{11} \\ \hline &\color{blue}{1}&\color{blue}{2}&\color{blue}{11}&\color{orangered}{11} \end{array} $$Bottom line represents the quotient $ \color{blue}{ x^{2}+2x+11 } $ with a remainder of $ \color{red}{ 11 } $.