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Another common definition of the exponential function to the natural basis, \(e^x\), comes from writing it as the series \(e^x = \sum_{k=0}^{\infty} \frac{x^k}{k!}\).

Complicated convolution operations become simple multiplications via the Laplace transform \(F(s) = \int_{-\infty}^{\infty}f(x)e^{-s x}dx\) for function \(f\).

Factorials apply only to nonnegative integers but can be extended to complex numbers with positive real parts using the Gamma function, \(\Gamma(n) = \int_0^\infty e^{-x}x^{n-1}dx\).