Answer
\[ = 12\]
Work Step by Step
\[\begin{gathered}
- \int_4^1 {2f\,\left( x \right)\,dx} \hfill \\
\hfill \\
rewrite \hfill \\
\hfill \\
= - 2\int_4^1 {f\,\left( x \right)} \,\,dx \hfill \\
\hfill \\
therefore \hfill \\
\hfill \\
= 2\int_1^4 {f\,\left( x \right)\,\,dx} \hfill \\
\hfill \\
where{\text{ }}\int_1^4 {f\,\left( x \right)\,\,dx} = 6 \hfill \\
\hfill \\
= 2\,\left( { 6} \right) \hfill \\
\hfill \\
= 12 \hfill \\
\hfill \\
\end{gathered} \]
