Divide using synthetic division $$ ( 2x^{2}+9x-5 ) \div ( 2x+1 ) $$
Answer
The synthetic division table is:
$$ \begin{array}{c|rrr}-1&2&9&-5\\& & -2& \color{black}{-7} \\ \hline &\color{blue}{2}&\color{blue}{7}&\color{orangered}{-12} \end{array} $$The solution is:
$$ \frac{ 2x^{2}+9x-5 }{ x+1 } = \color{blue}{2x+7} \color{red}{~-~} \frac{ \color{red}{ 12 } }{ x+1 } $$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.
$$ \begin{array}{c|rrr}\color{blue}{-1}&2&9&-5\\& & & \\ \hline &&& \end{array} $$Step 1 : Bring down the leading coefficient to the bottom row.
$$ \begin{array}{c|rrr}-1&\color{orangered}{ 2 }&9&-5\\& & & \\ \hline &\color{orangered}{2}&& \end{array} $$Step 2 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -1 } \cdot \color{blue}{ 2 } = \color{blue}{ -2 } $.
$$ \begin{array}{c|rrr}\color{blue}{-1}&2&9&-5\\& & \color{blue}{-2} & \\ \hline &\color{blue}{2}&& \end{array} $$Step 3 : Add down last column: $ \color{orangered}{ 9 } + \color{orangered}{ \left( -2 \right) } = \color{orangered}{ 7 } $
$$ \begin{array}{c|rrr}-1&2&\color{orangered}{ 9 }&-5\\& & \color{orangered}{-2} & \\ \hline &2&\color{orangered}{7}& \end{array} $$Step 4 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -1 } \cdot \color{blue}{ 7 } = \color{blue}{ -7 } $.
$$ \begin{array}{c|rrr}\color{blue}{-1}&2&9&-5\\& & -2& \color{blue}{-7} \\ \hline &2&\color{blue}{7}& \end{array} $$Step 5 : Add down last column: $ \color{orangered}{ -5 } + \color{orangered}{ \left( -7 \right) } = \color{orangered}{ -12 } $
$$ \begin{array}{c|rrr}-1&2&9&\color{orangered}{ -5 }\\& & -2& \color{orangered}{-7} \\ \hline &\color{blue}{2}&\color{blue}{7}&\color{orangered}{-12} \end{array} $$Bottom line represents the quotient $ \color{blue}{ 2x+7 } $ with a remainder of $ \color{red}{ -12 } $.