Divide using synthetic division $$ ( 2x^{3}-9x^{2}+9x-20 ) \div ( x-4 ) $$
Answer
The synthetic division table is:
$$ \begin{array}{c|rrrr}4&2&-9&9&-20\\& & 8& -4& \color{black}{20} \\ \hline &\color{blue}{2}&\color{blue}{-1}&\color{blue}{5}&\color{orangered}{0} \end{array} $$The solution is:
$$ \frac{ 2x^{3}-9x^{2}+9x-20 }{ x-4 } = \color{blue}{2x^{2}-x+5} $$Explanation
Step 1 : Write down the coefficients of the dividend into division table. Put the zero from $ x -4 = 0 $ ( $ x = \color{blue}{ 4 } $ ) at the left.
$$ \begin{array}{c|rrrr}\color{blue}{4}&2&-9&9&-20\\& & & & \\ \hline &&&& \end{array} $$Step 1 : Bring down the leading coefficient to the bottom row.
$$ \begin{array}{c|rrrr}4&\color{orangered}{ 2 }&-9&9&-20\\& & & & \\ \hline &\color{orangered}{2}&&& \end{array} $$Step 2 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ 4 } \cdot \color{blue}{ 2 } = \color{blue}{ 8 } $.
$$ \begin{array}{c|rrrr}\color{blue}{4}&2&-9&9&-20\\& & \color{blue}{8} & & \\ \hline &\color{blue}{2}&&& \end{array} $$Step 3 : Add down last column: $ \color{orangered}{ -9 } + \color{orangered}{ 8 } = \color{orangered}{ -1 } $
$$ \begin{array}{c|rrrr}4&2&\color{orangered}{ -9 }&9&-20\\& & \color{orangered}{8} & & \\ \hline &2&\color{orangered}{-1}&& \end{array} $$Step 4 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ 4 } \cdot \color{blue}{ \left( -1 \right) } = \color{blue}{ -4 } $.
$$ \begin{array}{c|rrrr}\color{blue}{4}&2&-9&9&-20\\& & 8& \color{blue}{-4} & \\ \hline &2&\color{blue}{-1}&& \end{array} $$Step 5 : Add down last column: $ \color{orangered}{ 9 } + \color{orangered}{ \left( -4 \right) } = \color{orangered}{ 5 } $
$$ \begin{array}{c|rrrr}4&2&-9&\color{orangered}{ 9 }&-20\\& & 8& \color{orangered}{-4} & \\ \hline &2&-1&\color{orangered}{5}& \end{array} $$Step 6 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ 4 } \cdot \color{blue}{ 5 } = \color{blue}{ 20 } $.
$$ \begin{array}{c|rrrr}\color{blue}{4}&2&-9&9&-20\\& & 8& -4& \color{blue}{20} \\ \hline &2&-1&\color{blue}{5}& \end{array} $$Step 7 : Add down last column: $ \color{orangered}{ -20 } + \color{orangered}{ 20 } = \color{orangered}{ 0 } $
$$ \begin{array}{c|rrrr}4&2&-9&9&\color{orangered}{ -20 }\\& & 8& -4& \color{orangered}{20} \\ \hline &\color{blue}{2}&\color{blue}{-1}&\color{blue}{5}&\color{orangered}{0} \end{array} $$Bottom line represents the quotient $ \color{blue}{ 2x^{2}-x+5 } $ with a remainder of $ \color{red}{ 0 } $.