Divide using synthetic division $$ ( x^{3}+5x^{2}+9x+45 ) \div ( x-3 ) $$
Answer
The synthetic division table is:
$$ \begin{array}{c|rrrr}3&1&5&9&45\\& & 3& 24& \color{black}{99} \\ \hline &\color{blue}{1}&\color{blue}{8}&\color{blue}{33}&\color{orangered}{144} \end{array} $$The solution is:
$$ \frac{ x^{3}+5x^{2}+9x+45 }{ x-3 } = \color{blue}{x^{2}+8x+33} ~+~ \frac{ \color{red}{ 144 } }{ x-3 } $$Explanation
Step 1 : Write down the coefficients of the dividend into division table. Put the zero from $ x -3 = 0 $ ( $ x = \color{blue}{ 3 } $ ) at the left.
$$ \begin{array}{c|rrrr}\color{blue}{3}&1&5&9&45\\& & & & \\ \hline &&&& \end{array} $$Step 1 : Bring down the leading coefficient to the bottom row.
$$ \begin{array}{c|rrrr}3&\color{orangered}{ 1 }&5&9&45\\& & & & \\ \hline &\color{orangered}{1}&&& \end{array} $$Step 2 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ 3 } \cdot \color{blue}{ 1 } = \color{blue}{ 3 } $.
$$ \begin{array}{c|rrrr}\color{blue}{3}&1&5&9&45\\& & \color{blue}{3} & & \\ \hline &\color{blue}{1}&&& \end{array} $$Step 3 : Add down last column: $ \color{orangered}{ 5 } + \color{orangered}{ 3 } = \color{orangered}{ 8 } $
$$ \begin{array}{c|rrrr}3&1&\color{orangered}{ 5 }&9&45\\& & \color{orangered}{3} & & \\ \hline &1&\color{orangered}{8}&& \end{array} $$Step 4 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ 3 } \cdot \color{blue}{ 8 } = \color{blue}{ 24 } $.
$$ \begin{array}{c|rrrr}\color{blue}{3}&1&5&9&45\\& & 3& \color{blue}{24} & \\ \hline &1&\color{blue}{8}&& \end{array} $$Step 5 : Add down last column: $ \color{orangered}{ 9 } + \color{orangered}{ 24 } = \color{orangered}{ 33 } $
$$ \begin{array}{c|rrrr}3&1&5&\color{orangered}{ 9 }&45\\& & 3& \color{orangered}{24} & \\ \hline &1&8&\color{orangered}{33}& \end{array} $$Step 6 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ 3 } \cdot \color{blue}{ 33 } = \color{blue}{ 99 } $.
$$ \begin{array}{c|rrrr}\color{blue}{3}&1&5&9&45\\& & 3& 24& \color{blue}{99} \\ \hline &1&8&\color{blue}{33}& \end{array} $$Step 7 : Add down last column: $ \color{orangered}{ 45 } + \color{orangered}{ 99 } = \color{orangered}{ 144 } $
$$ \begin{array}{c|rrrr}3&1&5&9&\color{orangered}{ 45 }\\& & 3& 24& \color{orangered}{99} \\ \hline &\color{blue}{1}&\color{blue}{8}&\color{blue}{33}&\color{orangered}{144} \end{array} $$Bottom line represents the quotient $ \color{blue}{ x^{2}+8x+33 } $ with a remainder of $ \color{red}{ 144 } $.