5.5 The Substitution Rule/1

Failed to parse (Conversion error. Server ("https://en.wikipedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle {\begin{aligned}&\int {e^{-x}}dx,\quad u=-x\\[2ex]&u=-x\\[2ex]&du=-dx\\[2ex]\end{aligned}}}

Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://en.wikipedia.org/api/rest_v1/":): {\displaystyle \int{e^{-x}} dx = -\int{e^{u}} du = -e^{u} +C = -e^{-x}+C }