极值点偏移

已知\(f(x)=x-lnx-1\),若\(f(x_1)=f(x_2)\neq0\)，求证：\(x_1+x_2>2\).
\(\psline(0,0)(2,2)(4,0)\)

 Title: Here is a title 
 A->B: Normal line 
 B-->C: Dashed line 
 C->>D: Open arrow 
 D-->>A: Dashed open arrow 

 st=>start: Start 
 io=>inputoutput: verification 
 op=>operation: Your Operation 
 cond=>condition: Yes or No? 
 e=>end

st->io->op->cond 
 cond(yes)->e 
 cond(no)->io 

start=>start: 开始
isLogin=>condition: 是否已登录？
login=>operation: 登陆
selectPic=>operation: 选择一张图片
isPic=>condition: 格式是否正确？
doIt=>operation: 完成资料
isRight=>condition: 资料是否符合要求？
end=>end: 完成

start->isLogin
isLogin(yes)->selectPic
isLogin(no)->login->selectPic
selectPic->isPic
isPic(yes)->doIt->isRight
isPic(no)->selectPic
isRight(yes)->end
isRight(no)->doIt1