The synthetic division table is:
$$ \begin{array}{c|rr}4&-10&-42\\& & \color{black}{-40} \\ \hline &\color{blue}{-10}&\color{orangered}{-82} \end{array} $$The solution is:
$$ \frac{ -10x-42 }{ x-4 } = \color{blue}{-10} \color{red}{~-~} \frac{ \color{red}{ 82 } }{ x-4 } $$Step 1 : Write down the coefficients of the dividend into division table. Put the zero from $ x -4 = 0 $ ( $ x = \color{blue}{ 4 } $ ) at the left.
$$ \begin{array}{c|rr}\color{blue}{4}&-10&-42\\& & \\ \hline && \end{array} $$Step 1 : Bring down the leading coefficient to the bottom row.
$$ \begin{array}{c|rr}4&\color{orangered}{ -10 }&-42\\& & \\ \hline &\color{orangered}{-10}& \end{array} $$Step 2 : Multiply by the number on the left, and carry the result into the next column: $ \color{blue}{ 4 } \cdot \color{blue}{ \left( -10 \right) } = \color{blue}{ -40 } $.
$$ \begin{array}{c|rr}\color{blue}{4}&-10&-42\\& & \color{blue}{-40} \\ \hline &\color{blue}{-10}& \end{array} $$Step 3 : Add down last column: $ \color{orangered}{ -42 } + \color{orangered}{ \left( -40 \right) } = \color{orangered}{ -82 } $
$$ \begin{array}{c|rr}4&-10&\color{orangered}{ -42 }\\& & \color{orangered}{-40} \\ \hline &\color{blue}{-10}&\color{orangered}{-82} \end{array} $$Bottom line represents the quotient $ \color{blue}{ -10 } $ with a remainder of $ \color{red}{ -82 } $.