Divide using synthetic division $$ ( 2x^{3}+15x^{2}+23x-4 ) \div ( x+5 ) $$
Answer
The synthetic division table is:
$$ \begin{array}{c|rrrr}-5&2&15&23&-4\\& & -10& -25& \color{black}{10} \\ \hline &\color{blue}{2}&\color{blue}{5}&\color{blue}{-2}&\color{orangered}{6} \end{array} $$The solution is:
$$ \frac{ 2x^{3}+15x^{2}+23x-4 }{ x+5 } = \color{blue}{2x^{2}+5x-2} ~+~ \frac{ \color{red}{ 6 } }{ x+5 } $$Explanation
Step 1 : Write down the coefficients of the dividend into division table. Put the zero from $ x + 5 = 0 $ ( $ x = \color{blue}{ -5 } $ ) at the left.
$$ \begin{array}{c|rrrr}\color{blue}{-5}&2&15&23&-4\\& & & & \\ \hline &&&& \end{array} $$Step 1 : Bring down the leading coefficient to the bottom row.
$$ \begin{array}{c|rrrr}-5&\color{orangered}{ 2 }&15&23&-4\\& & & & \\ \hline &\color{orangered}{2}&&& \end{array} $$Step 2 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -5 } \cdot \color{blue}{ 2 } = \color{blue}{ -10 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-5}&2&15&23&-4\\& & \color{blue}{-10} & & \\ \hline &\color{blue}{2}&&& \end{array} $$Step 3 : Add down last column: $ \color{orangered}{ 15 } + \color{orangered}{ \left( -10 \right) } = \color{orangered}{ 5 } $
$$ \begin{array}{c|rrrr}-5&2&\color{orangered}{ 15 }&23&-4\\& & \color{orangered}{-10} & & \\ \hline &2&\color{orangered}{5}&& \end{array} $$Step 4 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -5 } \cdot \color{blue}{ 5 } = \color{blue}{ -25 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-5}&2&15&23&-4\\& & -10& \color{blue}{-25} & \\ \hline &2&\color{blue}{5}&& \end{array} $$Step 5 : Add down last column: $ \color{orangered}{ 23 } + \color{orangered}{ \left( -25 \right) } = \color{orangered}{ -2 } $
$$ \begin{array}{c|rrrr}-5&2&15&\color{orangered}{ 23 }&-4\\& & -10& \color{orangered}{-25} & \\ \hline &2&5&\color{orangered}{-2}& \end{array} $$Step 6 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -5 } \cdot \color{blue}{ \left( -2 \right) } = \color{blue}{ 10 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-5}&2&15&23&-4\\& & -10& -25& \color{blue}{10} \\ \hline &2&5&\color{blue}{-2}& \end{array} $$Step 7 : Add down last column: $ \color{orangered}{ -4 } + \color{orangered}{ 10 } = \color{orangered}{ 6 } $
$$ \begin{array}{c|rrrr}-5&2&15&23&\color{orangered}{ -4 }\\& & -10& -25& \color{orangered}{10} \\ \hline &\color{blue}{2}&\color{blue}{5}&\color{blue}{-2}&\color{orangered}{6} \end{array} $$Bottom line represents the quotient $ \color{blue}{ 2x^{2}+5x-2 } $ with a remainder of $ \color{red}{ 6 } $.