Exponential distribution

ATTENTION - instead of a decimal comma should be used decimal DOT !

**Formulas**
$X\sim Exp(\lambda)$	$P(x)=\left\{\begin{matrix} \lambda e^{-\lambda x} & ... & x\geq 0\\ & & \\ 0 & ... & x< 0\end{matrix}\right.$
$E(X)=\frac{1}{\lambda }$	$D(X)=\frac{1}{\lambda^{2} }$
$\gamma _{1}=2$	$\gamma _{2}=6$