Let X be the random variable with the density function f(x)\displaystyle {f{{\left({x}\right)}}} given by
f(x)={8.1(1+x)9.1ifx≥00otherwise\displaystyle {f{{\left({x}\right)}}}={\left\lbrace\begin{array}{ccc} {\frac{{{8.1}}}{{{\left({1}+{x}\right)}^{{{9.1}}}}}}&\text{if}&{x}\geq{0}\\{0}&&\text{otherwise}\end{array}\right.}
Find the mean of X.  
Find the variance of X.  

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