设函数 f(x)=lnxx+1f\left( x\right) = \frac{\ln x}{x + 1}f(x)=x+1lnx 的极值点为 x0{x}_{0}x0 ,则 x0f(x0)={x}_{0}f\left( {x}_{0}\right) =x0f(x0)= ___. 已知数列 {an}\left\{ {a}_{n}\right\}{an} 满足 an+1=ean+1{a}_{n + 1} = {\mathrm{e}}^{{a}_{n} + 1}an+1=ean+1 ,若 x0(a2+1)=lna4{x}_{0}\left( {{a}_{2} + 1}\right) = \ln {a}_{4}x0(a2+1)=lna4 ,则 a1+a2={a}_{1} + {a}_{2} =a1+a2= ___.