Divide using synthetic division $$ ( 3x^{2}+14x-15 ) \div ( x+6 ) $$
Answer
The synthetic division table is:
$$ \begin{array}{c|rrr}-6&3&14&-15\\& & -18& \color{black}{24} \\ \hline &\color{blue}{3}&\color{blue}{-4}&\color{orangered}{9} \end{array} $$The solution is:
$$ \frac{ 3x^{2}+14x-15 }{ x+6 } = \color{blue}{3x-4} ~+~ \frac{ \color{red}{ 9 } }{ x+6 } $$Explanation
Step 1 : Write down the coefficients of the dividend into division table. Put the zero from $ x + 6 = 0 $ ( $ x = \color{blue}{ -6 } $ ) at the left.
$$ \begin{array}{c|rrr}\color{blue}{-6}&3&14&-15\\& & & \\ \hline &&& \end{array} $$Step 1 : Bring down the leading coefficient to the bottom row.
$$ \begin{array}{c|rrr}-6&\color{orangered}{ 3 }&14&-15\\& & & \\ \hline &\color{orangered}{3}&& \end{array} $$Step 2 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -6 } \cdot \color{blue}{ 3 } = \color{blue}{ -18 } $.
$$ \begin{array}{c|rrr}\color{blue}{-6}&3&14&-15\\& & \color{blue}{-18} & \\ \hline &\color{blue}{3}&& \end{array} $$Step 3 : Add down last column: $ \color{orangered}{ 14 } + \color{orangered}{ \left( -18 \right) } = \color{orangered}{ -4 } $
$$ \begin{array}{c|rrr}-6&3&\color{orangered}{ 14 }&-15\\& & \color{orangered}{-18} & \\ \hline &3&\color{orangered}{-4}& \end{array} $$Step 4 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -6 } \cdot \color{blue}{ \left( -4 \right) } = \color{blue}{ 24 } $.
$$ \begin{array}{c|rrr}\color{blue}{-6}&3&14&-15\\& & -18& \color{blue}{24} \\ \hline &3&\color{blue}{-4}& \end{array} $$Step 5 : Add down last column: $ \color{orangered}{ -15 } + \color{orangered}{ 24 } = \color{orangered}{ 9 } $
$$ \begin{array}{c|rrr}-6&3&14&\color{orangered}{ -15 }\\& & -18& \color{orangered}{24} \\ \hline &\color{blue}{3}&\color{blue}{-4}&\color{orangered}{9} \end{array} $$Bottom line represents the quotient $ \color{blue}{ 3x-4 } $ with a remainder of $ \color{red}{ 9 } $.