6.
已知函数\(f\left( x \right)=\dfrac{-{{x}^{2}}+ax-a}{{{e}^{x}}}(x > 0,a\in R)\).
\((1)\)当\(a=1\)时,求函数\(f\left( x \right)\)的极值;
\((2)\)设\(g\left( x \right)=\dfrac{f\left( x \right)+{f}{{{'}}}\left( x \right)}{x-1}\),若函数\(g\left( x \right)\)在\(\left( 0,1 \right)\cup \left( 1,+\infty \right)\)内有两个极值点\({{x}_{1}},{{x}_{2}}\),求证: \(g\left( {{x}_{1}} \right)\cdot g\left( {{x}_{2}} \right) < \dfrac{4}{{{e}^{2}}}\).