\begin{eqnarray*}f'\left(x\right) & = & -\left[\int_{0}^{x}\,f\left\t\right)\,dt+x\,f\left(x\right)\right]+x\,f\left(x\right)\\& = & -\int_{0}^{x}\,f
\begin{eqnarray*}f'\left(x\right) & = & -\left[\int_{0}^{x}\,f\left(t\right)\,dt+x\,f\left(x\right)\right]+x\,f\left(x\right)\\& = & -\int_{0}^{x}\,f\left(t\right)\,dt\end{eqnarray*}