TeX source:
\begin{array}{lclcrcl}\quad\mathbb{D}&=&\mathbb{R}\setminus_{\{-2\}} \cr \cr f(x) &=& \dfrac{1}{2x+4} \cr \cr \quad u(x) &=& 1 & \Rightarrow & u'(x) &=& 0 \cr \quad v(x) &=& 2x+4 & \Rightarrow & v'(x) &=& 2\cr \cr f'(x) &=& \dfrac{0 \cdot (2x+4)-1 \cdot 2}{(2x+4)^2} \cr \cr &=& \dfrac{-2}{4x^2+16x+16} \cr \cr &=& -\dfrac{2}{2(2x^2+8x+8)} \cr \cr &=& -\dfrac{1}{2x^2+8x+8} \end{array}