How to identify family of function from given property












2














A={$f:Rto R$}



with following properties



f has derivative of every order



$forall x,yin R$ $f(x+y)-f(y-x)=2xf'(y)$



then I have to find whole family



Till now I just able to show $f(x)-f(-x)/2x=2xf'(0)$



I wanted to solve this problem.



Please provide just hint..



Thanks in Advanced










share|cite|improve this question






















  • Plug $y = x$ into the equation and use Taylor series ($f$ has a Taylor series since it's infinitely differentiable).
    – Rchn
    Nov 27 at 13:46












  • Sir I have done that , I got f(y)=f(0)+yf'(y/2).
    – MathLover
    Nov 27 at 13:53










  • form here how I one identify given family is polynomial of degree less than 2
    – MathLover
    Nov 27 at 13:54
















2














A={$f:Rto R$}



with following properties



f has derivative of every order



$forall x,yin R$ $f(x+y)-f(y-x)=2xf'(y)$



then I have to find whole family



Till now I just able to show $f(x)-f(-x)/2x=2xf'(0)$



I wanted to solve this problem.



Please provide just hint..



Thanks in Advanced










share|cite|improve this question






















  • Plug $y = x$ into the equation and use Taylor series ($f$ has a Taylor series since it's infinitely differentiable).
    – Rchn
    Nov 27 at 13:46












  • Sir I have done that , I got f(y)=f(0)+yf'(y/2).
    – MathLover
    Nov 27 at 13:53










  • form here how I one identify given family is polynomial of degree less than 2
    – MathLover
    Nov 27 at 13:54














2












2








2







A={$f:Rto R$}



with following properties



f has derivative of every order



$forall x,yin R$ $f(x+y)-f(y-x)=2xf'(y)$



then I have to find whole family



Till now I just able to show $f(x)-f(-x)/2x=2xf'(0)$



I wanted to solve this problem.



Please provide just hint..



Thanks in Advanced










share|cite|improve this question













A={$f:Rto R$}



with following properties



f has derivative of every order



$forall x,yin R$ $f(x+y)-f(y-x)=2xf'(y)$



then I have to find whole family



Till now I just able to show $f(x)-f(-x)/2x=2xf'(0)$



I wanted to solve this problem.



Please provide just hint..



Thanks in Advanced







real-analysis derivatives






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Nov 27 at 13:28









MathLover

45710




45710












  • Plug $y = x$ into the equation and use Taylor series ($f$ has a Taylor series since it's infinitely differentiable).
    – Rchn
    Nov 27 at 13:46












  • Sir I have done that , I got f(y)=f(0)+yf'(y/2).
    – MathLover
    Nov 27 at 13:53










  • form here how I one identify given family is polynomial of degree less than 2
    – MathLover
    Nov 27 at 13:54


















  • Plug $y = x$ into the equation and use Taylor series ($f$ has a Taylor series since it's infinitely differentiable).
    – Rchn
    Nov 27 at 13:46












  • Sir I have done that , I got f(y)=f(0)+yf'(y/2).
    – MathLover
    Nov 27 at 13:53










  • form here how I one identify given family is polynomial of degree less than 2
    – MathLover
    Nov 27 at 13:54
















Plug $y = x$ into the equation and use Taylor series ($f$ has a Taylor series since it's infinitely differentiable).
– Rchn
Nov 27 at 13:46






Plug $y = x$ into the equation and use Taylor series ($f$ has a Taylor series since it's infinitely differentiable).
– Rchn
Nov 27 at 13:46














Sir I have done that , I got f(y)=f(0)+yf'(y/2).
– MathLover
Nov 27 at 13:53




Sir I have done that , I got f(y)=f(0)+yf'(y/2).
– MathLover
Nov 27 at 13:53












form here how I one identify given family is polynomial of degree less than 2
– MathLover
Nov 27 at 13:54




form here how I one identify given family is polynomial of degree less than 2
– MathLover
Nov 27 at 13:54















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