Answer:
[tex] \qquad\quad\hookrightarrow{\sf { 1000(e-1)}}[/tex]
Solution:
[tex] \begin{aligned}&\longrightarrow \int_{0} ^{1000} {e}^{ - |x| }dx = \sum_{k = 0}^{999} \int_{k}^{k + 1}e ^{x - |x| }dx \\ \\ &\longrightarrow\int_{0} ^{1000} {e}^{ - |x| }dx = \sum_{k = 0}^{999} \int_{k}^{k + 1}e^{x - k}dx \\\\&\longrightarrow\int_{0} ^{1000} {e}^{ - |x| }dx = \sum_{k = 0}^{999}e^{x - k \big |_{k}^ {k + 1}} \\ \\& \longrightarrow\int_{0} ^{1000} {e}^{ - |x| }dx = \sum_{k = 0}^ {999}(e - 1)\\\\&\longrightarrow\int_{0} ^{1000} {e}^{ - |x| }dx = 1000(e - 1)\end{aligned}[/tex]
