Find remainder when $ 2x^{3}-3x^{2}-50x+75 $ is divided by $ x+1 $.
Answer
The synthetic division table is:
$$ \begin{array}{c|rrrr}-1&2&-3&-50&75\\& & -2& 5& \color{black}{45} \\ \hline &\color{blue}{2}&\color{blue}{-5}&\color{blue}{-45}&\color{orangered}{120} \end{array} $$The remainder when $ 2x^{3}-3x^{2}-50x+75 $ is divided by $ x+1 $ is $ \, \color{red}{ 120 } $.
Explanation
We can find remainder using synthetic division method.
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.
$$ \begin{array}{c|rrrr}\color{blue}{-1}&2&-3&-50&75\\& & & & \\ \hline &&&& \end{array} $$Step 1 : Bring down the leading coefficient to the bottom row.
$$ \begin{array}{c|rrrr}-1&\color{orangered}{ 2 }&-3&-50&75\\& & & & \\ \hline &\color{orangered}{2}&&& \end{array} $$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 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-1}&2&-3&-50&75\\& & \color{blue}{-2} & & \\ \hline &\color{blue}{2}&&& \end{array} $$Step 3 : Add down last column: $ \color{orangered}{ -3 } + \color{orangered}{ \left( -2 \right) } = \color{orangered}{ -5 } $
$$ \begin{array}{c|rrrr}-1&2&\color{orangered}{ -3 }&-50&75\\& & \color{orangered}{-2} & & \\ \hline &2&\color{orangered}{-5}&& \end{array} $$Step 4 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -1 } \cdot \color{blue}{ \left( -5 \right) } = \color{blue}{ 5 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-1}&2&-3&-50&75\\& & -2& \color{blue}{5} & \\ \hline &2&\color{blue}{-5}&& \end{array} $$Step 5 : Add down last column: $ \color{orangered}{ -50 } + \color{orangered}{ 5 } = \color{orangered}{ -45 } $
$$ \begin{array}{c|rrrr}-1&2&-3&\color{orangered}{ -50 }&75\\& & -2& \color{orangered}{5} & \\ \hline &2&-5&\color{orangered}{-45}& \end{array} $$Step 6 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ -1 } \cdot \color{blue}{ \left( -45 \right) } = \color{blue}{ 45 } $.
$$ \begin{array}{c|rrrr}\color{blue}{-1}&2&-3&-50&75\\& & -2& 5& \color{blue}{45} \\ \hline &2&-5&\color{blue}{-45}& \end{array} $$Step 7 : Add down last column: $ \color{orangered}{ 75 } + \color{orangered}{ 45 } = \color{orangered}{ 120 } $
$$ \begin{array}{c|rrrr}-1&2&-3&-50&\color{orangered}{ 75 }\\& & -2& 5& \color{orangered}{45} \\ \hline &\color{blue}{2}&\color{blue}{-5}&\color{blue}{-45}&\color{orangered}{120} \end{array} $$Remainder is the last entry in the bottom row $ \left(\color{red}{ 120 }\right) $.