The relation to use is \begin{align} \frac{d}{dx} \left[ x^{\
u} J_{\
u}(x) \right] = x^{\
u} J_{\
u-1}(x). \end{align} Integrating both sides with respect to $x$ yields \begin{align} \int \frac{d}{dx} \left[ x^{\
u} J_{\
u}(x) \right] \ dx &= \int x^{\
u} J_{\
u-1}(x) \ dx \end{align} or \begin{align} \int x^{\
u} J_{\
u-1}(x) = x^{\
u} J_{\
u}(x) + \mbox{ constant }. \end{align} which provides the desired result.