Question: $\int_{4}^{5} e^{x} d x$
Solution:
Let $I=\int_{4}^{5} e^{x} d x$
$\int e^{x} d x=e^{x}=\mathrm{F}(x)$
By second fundamental theorem of calculus, we obtain
$\begin{aligned} I &=\mathrm{F}(5)-\mathrm{F}(4) \\ &=e^{5}-e^{4} \\ &=e^{4}(e-1) \end{aligned}$
