Divide using synthetic division $$ ( x^{3}+17x^{2}+70x-54 ) \div ( x+1 ) $$
Answer
The synthetic division table is:
$$ \begin{array}{c|rrrr}-1&1&17&70&-54\\& & -1& -16& \color{black}{-54} \\ \hline &\color{blue}{1}&\color{blue}{16}&\color{blue}{54}&\color{orangered}{-108} \end{array} $$The solution is:
$$ \frac{ x^{3}+17x^{2}+70x-54 }{ x+1 } = \color{blue}{x^{2}+16x+54} \color{red}{~-~} \frac{ \color{red}{ 108 } }{ x+1 } $$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.
$$ \begin{array}{c|rrrr}\color{blue}{-1}&1&17&70&-54\\& & & & \\ \hline &&&& \end{array} $$Step 1 : Bring down the leading coefficient to the bottom row.
$$ \begin{array}{c|rrrr}-1&\color{orangered}{ 1 }&17&70&-54\\& & & & \\ \hline &\color{orangered}{1}&&& \end{array} $$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 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-1}&1&17&70&-54\\& & \color{blue}{-1} & & \\ \hline &\color{blue}{1}&&& \end{array} $$Step 3 : Add down last column: $ \color{orangered}{ 17 } + \color{orangered}{ \left( -1 \right) } = \color{orangered}{ 16 } $
$$ \begin{array}{c|rrrr}-1&1&\color{orangered}{ 17 }&70&-54\\& & \color{orangered}{-1} & & \\ \hline &1&\color{orangered}{16}&& \end{array} $$Step 4 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -1 } \cdot \color{blue}{ 16 } = \color{blue}{ -16 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-1}&1&17&70&-54\\& & -1& \color{blue}{-16} & \\ \hline &1&\color{blue}{16}&& \end{array} $$Step 5 : Add down last column: $ \color{orangered}{ 70 } + \color{orangered}{ \left( -16 \right) } = \color{orangered}{ 54 } $
$$ \begin{array}{c|rrrr}-1&1&17&\color{orangered}{ 70 }&-54\\& & -1& \color{orangered}{-16} & \\ \hline &1&16&\color{orangered}{54}& \end{array} $$Step 6 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -1 } \cdot \color{blue}{ 54 } = \color{blue}{ -54 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-1}&1&17&70&-54\\& & -1& -16& \color{blue}{-54} \\ \hline &1&16&\color{blue}{54}& \end{array} $$Step 7 : Add down last column: $ \color{orangered}{ -54 } + \color{orangered}{ \left( -54 \right) } = \color{orangered}{ -108 } $
$$ \begin{array}{c|rrrr}-1&1&17&70&\color{orangered}{ -54 }\\& & -1& -16& \color{orangered}{-54} \\ \hline &\color{blue}{1}&\color{blue}{16}&\color{blue}{54}&\color{orangered}{-108} \end{array} $$Bottom line represents the quotient $ \color{blue}{ x^{2}+16x+54 } $ with a remainder of $ \color{red}{ -108 } $.