If $f(0)=0$ and $f(1)=1$ there exists $(x_i)$ such that $sumlimits_{i=1}^nfrac{1}{f'(x_i)}=n$












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Let $f:[0,1] tomathbb R$ be differentiable, with $f(0)=0$ and $f(1)=1 $. Prove that, for every $nin mathbb N$, there exists $x_1,x_2,ldots,x_nin[0,1]$ such that $$sum_{i=1}^nfrac{1}{f'(x_i)}=n$$










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  • $begingroup$
    i use Mean value theorem to find f'.yes i prove for n=1
    $endgroup$
    – M.H
    Feb 2 '13 at 17:31
















1












$begingroup$


Let $f:[0,1] tomathbb R$ be differentiable, with $f(0)=0$ and $f(1)=1 $. Prove that, for every $nin mathbb N$, there exists $x_1,x_2,ldots,x_nin[0,1]$ such that $$sum_{i=1}^nfrac{1}{f'(x_i)}=n$$










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$endgroup$












  • $begingroup$
    i use Mean value theorem to find f'.yes i prove for n=1
    $endgroup$
    – M.H
    Feb 2 '13 at 17:31














1












1








1





$begingroup$


Let $f:[0,1] tomathbb R$ be differentiable, with $f(0)=0$ and $f(1)=1 $. Prove that, for every $nin mathbb N$, there exists $x_1,x_2,ldots,x_nin[0,1]$ such that $$sum_{i=1}^nfrac{1}{f'(x_i)}=n$$










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$endgroup$




Let $f:[0,1] tomathbb R$ be differentiable, with $f(0)=0$ and $f(1)=1 $. Prove that, for every $nin mathbb N$, there exists $x_1,x_2,ldots,x_nin[0,1]$ such that $$sum_{i=1}^nfrac{1}{f'(x_i)}=n$$







sequences-and-series analysis






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edited Jan 11 at 21:58









Did

248k23223460




248k23223460










asked Feb 2 '13 at 17:22









M.HM.H

7,28711554




7,28711554












  • $begingroup$
    i use Mean value theorem to find f'.yes i prove for n=1
    $endgroup$
    – M.H
    Feb 2 '13 at 17:31


















  • $begingroup$
    i use Mean value theorem to find f'.yes i prove for n=1
    $endgroup$
    – M.H
    Feb 2 '13 at 17:31
















$begingroup$
i use Mean value theorem to find f'.yes i prove for n=1
$endgroup$
– M.H
Feb 2 '13 at 17:31




$begingroup$
i use Mean value theorem to find f'.yes i prove for n=1
$endgroup$
– M.H
Feb 2 '13 at 17:31










1 Answer
1






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4












$begingroup$

By the mean value theorem, there exists $x$ such that $f(1)-f(0)=f'(x)(1-0)$. Take $x_i=x$ for every $igeqslant1$.






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$endgroup$









  • 1




    $begingroup$
    You mean the mean value theorem, not the intermediate value theorem.
    $endgroup$
    – Chris Eagle
    Feb 2 '13 at 17:27










  • $begingroup$
    @ChrisEagle Indeed I do. Thanks.
    $endgroup$
    – Did
    Feb 2 '13 at 17:28










  • $begingroup$
    @did:thanks sir
    $endgroup$
    – M.H
    Feb 2 '13 at 17:36











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1 Answer
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active

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1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









4












$begingroup$

By the mean value theorem, there exists $x$ such that $f(1)-f(0)=f'(x)(1-0)$. Take $x_i=x$ for every $igeqslant1$.






share|cite|improve this answer









$endgroup$









  • 1




    $begingroup$
    You mean the mean value theorem, not the intermediate value theorem.
    $endgroup$
    – Chris Eagle
    Feb 2 '13 at 17:27










  • $begingroup$
    @ChrisEagle Indeed I do. Thanks.
    $endgroup$
    – Did
    Feb 2 '13 at 17:28










  • $begingroup$
    @did:thanks sir
    $endgroup$
    – M.H
    Feb 2 '13 at 17:36
















4












$begingroup$

By the mean value theorem, there exists $x$ such that $f(1)-f(0)=f'(x)(1-0)$. Take $x_i=x$ for every $igeqslant1$.






share|cite|improve this answer









$endgroup$









  • 1




    $begingroup$
    You mean the mean value theorem, not the intermediate value theorem.
    $endgroup$
    – Chris Eagle
    Feb 2 '13 at 17:27










  • $begingroup$
    @ChrisEagle Indeed I do. Thanks.
    $endgroup$
    – Did
    Feb 2 '13 at 17:28










  • $begingroup$
    @did:thanks sir
    $endgroup$
    – M.H
    Feb 2 '13 at 17:36














4












4








4





$begingroup$

By the mean value theorem, there exists $x$ such that $f(1)-f(0)=f'(x)(1-0)$. Take $x_i=x$ for every $igeqslant1$.






share|cite|improve this answer









$endgroup$



By the mean value theorem, there exists $x$ such that $f(1)-f(0)=f'(x)(1-0)$. Take $x_i=x$ for every $igeqslant1$.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Feb 2 '13 at 17:25









DidDid

248k23223460




248k23223460








  • 1




    $begingroup$
    You mean the mean value theorem, not the intermediate value theorem.
    $endgroup$
    – Chris Eagle
    Feb 2 '13 at 17:27










  • $begingroup$
    @ChrisEagle Indeed I do. Thanks.
    $endgroup$
    – Did
    Feb 2 '13 at 17:28










  • $begingroup$
    @did:thanks sir
    $endgroup$
    – M.H
    Feb 2 '13 at 17:36














  • 1




    $begingroup$
    You mean the mean value theorem, not the intermediate value theorem.
    $endgroup$
    – Chris Eagle
    Feb 2 '13 at 17:27










  • $begingroup$
    @ChrisEagle Indeed I do. Thanks.
    $endgroup$
    – Did
    Feb 2 '13 at 17:28










  • $begingroup$
    @did:thanks sir
    $endgroup$
    – M.H
    Feb 2 '13 at 17:36








1




1




$begingroup$
You mean the mean value theorem, not the intermediate value theorem.
$endgroup$
– Chris Eagle
Feb 2 '13 at 17:27




$begingroup$
You mean the mean value theorem, not the intermediate value theorem.
$endgroup$
– Chris Eagle
Feb 2 '13 at 17:27












$begingroup$
@ChrisEagle Indeed I do. Thanks.
$endgroup$
– Did
Feb 2 '13 at 17:28




$begingroup$
@ChrisEagle Indeed I do. Thanks.
$endgroup$
– Did
Feb 2 '13 at 17:28












$begingroup$
@did:thanks sir
$endgroup$
– M.H
Feb 2 '13 at 17:36




$begingroup$
@did:thanks sir
$endgroup$
– M.H
Feb 2 '13 at 17:36


















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