∫ e − x d x , u = − x u = − x d u = − d x ∫ e − x d x = − ∫ e u d u = − e u d u = − e − x + C {\displaystyle {\begin{aligned}&\int {e^{-x}}dx,u=-x\\[2ex]&u=-x\\[2ex]&du=-dx\\[2ex]&\int {e^{-x}}dx=\\[2ex]-\int {e^{u}}du=\\[2ex]-e^{u}du=\\[2ex]-e^{-x}+C\end{aligned}}}
![{\displaystyle {\begin{aligned}&\int {e^{-x}}dx,u=-x\\[2ex]&u=-x\\[2ex]&du=-dx\\[2ex]&\int {e^{-x}}dx=\\[2ex]-\int {e^{u}}du=\\[2ex]-e^{u}du=\\[2ex]-e^{-x}+C\end{aligned}}}](https://en.wikipedia.org/api/rest_v1/media/math/render/svg/ebb584f8370d8145a4d2c6e7f62b66456920a75f)