Divide using synthetic division $$ ( x^{3}+7x^{2}+2x-40 ) \div ( x-2 ) $$
Answer
The synthetic division table is:
$$ \begin{array}{c|rrrr}2&1&7&2&-40\\& & 2& 18& \color{black}{40} \\ \hline &\color{blue}{1}&\color{blue}{9}&\color{blue}{20}&\color{orangered}{0} \end{array} $$The solution is:
$$ \frac{ x^{3}+7x^{2}+2x-40 }{ x-2 } = \color{blue}{x^{2}+9x+20} $$Explanation
Step 1 : Write down the coefficients of the dividend into division table. Put the zero from $ x -2 = 0 $ ( $ x = \color{blue}{ 2 } $ ) at the left.
$$ \begin{array}{c|rrrr}\color{blue}{2}&1&7&2&-40\\& & & & \\ \hline &&&& \end{array} $$Step 1 : Bring down the leading coefficient to the bottom row.
$$ \begin{array}{c|rrrr}2&\color{orangered}{ 1 }&7&2&-40\\& & & & \\ \hline &\color{orangered}{1}&&& \end{array} $$Step 2 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ 2 } \cdot \color{blue}{ 1 } = \color{blue}{ 2 } $.
$$ \begin{array}{c|rrrr}\color{blue}{2}&1&7&2&-40\\& & \color{blue}{2} & & \\ \hline &\color{blue}{1}&&& \end{array} $$Step 3 : Add down last column: $ \color{orangered}{ 7 } + \color{orangered}{ 2 } = \color{orangered}{ 9 } $
$$ \begin{array}{c|rrrr}2&1&\color{orangered}{ 7 }&2&-40\\& & \color{orangered}{2} & & \\ \hline &1&\color{orangered}{9}&& \end{array} $$Step 4 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ 2 } \cdot \color{blue}{ 9 } = \color{blue}{ 18 } $.
$$ \begin{array}{c|rrrr}\color{blue}{2}&1&7&2&-40\\& & 2& \color{blue}{18} & \\ \hline &1&\color{blue}{9}&& \end{array} $$Step 5 : Add down last column: $ \color{orangered}{ 2 } + \color{orangered}{ 18 } = \color{orangered}{ 20 } $
$$ \begin{array}{c|rrrr}2&1&7&\color{orangered}{ 2 }&-40\\& & 2& \color{orangered}{18} & \\ \hline &1&9&\color{orangered}{20}& \end{array} $$Step 6 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ 2 } \cdot \color{blue}{ 20 } = \color{blue}{ 40 } $.
$$ \begin{array}{c|rrrr}\color{blue}{2}&1&7&2&-40\\& & 2& 18& \color{blue}{40} \\ \hline &1&9&\color{blue}{20}& \end{array} $$Step 7 : Add down last column: $ \color{orangered}{ -40 } + \color{orangered}{ 40 } = \color{orangered}{ 0 } $
$$ \begin{array}{c|rrrr}2&1&7&2&\color{orangered}{ -40 }\\& & 2& 18& \color{orangered}{40} \\ \hline &\color{blue}{1}&\color{blue}{9}&\color{blue}{20}&\color{orangered}{0} \end{array} $$Bottom line represents the quotient $ \color{blue}{ x^{2}+9x+20 } $ with a remainder of $ \color{red}{ 0 } $.