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Find functions f & g such that f(x+y)=g (x.y) for all x & y?


How do you define functions for non-mathematicians?Automated generation of a parametric plot?For each $y in mathbb{R}$ either no $x$ with $f(x) = y$ or two such values of $x$. Show that $f$ is discontinuous.Show that if $C(K)$ is separable, then $K$ is metrisable, for $K$ compact and HausdorffFinding Conjugate harmonic of $u = frac{1}{2} ln(x^2 + y^2)$Asymptotic functions with derivatives that are $1/2^x$Nowhere Differentiable function over a non-compact spaceMethod for deconstructing an integral involving two functionsFinding derivative given $f(x)$ and limitfix point solution or approximation available? logistic regression?













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My approach towards this question was that first I putted x=0 and then y=0 which yields f(x)=f(y)and f(x)=g(0), and again for x=1 & y=1 it gives g (x)=f(1+x), and so on. My query is that what should the compact & rigorous form of proof or solution looks like because I found myself stuck between results and not comprehending results very well. Thanks.










share|cite|improve this question











$endgroup$

















    2












    $begingroup$


    My approach towards this question was that first I putted x=0 and then y=0 which yields f(x)=f(y)and f(x)=g(0), and again for x=1 & y=1 it gives g (x)=f(1+x), and so on. My query is that what should the compact & rigorous form of proof or solution looks like because I found myself stuck between results and not comprehending results very well. Thanks.










    share|cite|improve this question











    $endgroup$















      2












      2








      2


      1



      $begingroup$


      My approach towards this question was that first I putted x=0 and then y=0 which yields f(x)=f(y)and f(x)=g(0), and again for x=1 & y=1 it gives g (x)=f(1+x), and so on. My query is that what should the compact & rigorous form of proof or solution looks like because I found myself stuck between results and not comprehending results very well. Thanks.










      share|cite|improve this question











      $endgroup$




      My approach towards this question was that first I putted x=0 and then y=0 which yields f(x)=f(y)and f(x)=g(0), and again for x=1 & y=1 it gives g (x)=f(1+x), and so on. My query is that what should the compact & rigorous form of proof or solution looks like because I found myself stuck between results and not comprehending results very well. Thanks.







      real-analysis calculus functional-analysis functions






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      share|cite|improve this question













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      share|cite|improve this question








      edited 1 hour ago







      BORN TO LEARN

















      asked 2 hours ago









      BORN TO LEARNBORN TO LEARN

      377




      377






















          1 Answer
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          $begingroup$

          $$f(x) = f(x + 0) = g(x cdot 0) = g(0)$$ for all $x$. Thus $f(x)$ is constant and always equal to $g(0)$. Moreover, $$g(0) = f(1 + y) = g(1 cdot y) = g(y)$$ for all $y$. Thus $g$ is also constant and equal to $g(0)$. Thus $f, g$ are the same constant function. All constant functions $f = g = c$ will satisfy the relation. This is all you need.






          share|cite|improve this answer









          $endgroup$









          • 1




            $begingroup$
            Yeah thanks man m looking for this kind of preciseness.
            $endgroup$
            – BORN TO LEARN
            2 hours ago










          • $begingroup$
            Sorry I edited it because I made a mistake in description that g(x)=f(1+y) instead of g(x)=f(1+x).
            $endgroup$
            – BORN TO LEARN
            1 hour ago










          • $begingroup$
            Now I think your proof also needs editing?
            $endgroup$
            – BORN TO LEARN
            1 hour ago










          • $begingroup$
            @BORNTOLEARN where does it need edited? I only used the relation f(x + y) = g(x y).
            $endgroup$
            – BenB
            1 hour ago






          • 1




            $begingroup$
            @BORNTOLEARN because f is identically equal to g(0) as I show in the previous part.
            $endgroup$
            – BenB
            1 hour ago












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          active

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          active

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          4












          $begingroup$

          $$f(x) = f(x + 0) = g(x cdot 0) = g(0)$$ for all $x$. Thus $f(x)$ is constant and always equal to $g(0)$. Moreover, $$g(0) = f(1 + y) = g(1 cdot y) = g(y)$$ for all $y$. Thus $g$ is also constant and equal to $g(0)$. Thus $f, g$ are the same constant function. All constant functions $f = g = c$ will satisfy the relation. This is all you need.






          share|cite|improve this answer









          $endgroup$









          • 1




            $begingroup$
            Yeah thanks man m looking for this kind of preciseness.
            $endgroup$
            – BORN TO LEARN
            2 hours ago










          • $begingroup$
            Sorry I edited it because I made a mistake in description that g(x)=f(1+y) instead of g(x)=f(1+x).
            $endgroup$
            – BORN TO LEARN
            1 hour ago










          • $begingroup$
            Now I think your proof also needs editing?
            $endgroup$
            – BORN TO LEARN
            1 hour ago










          • $begingroup$
            @BORNTOLEARN where does it need edited? I only used the relation f(x + y) = g(x y).
            $endgroup$
            – BenB
            1 hour ago






          • 1




            $begingroup$
            @BORNTOLEARN because f is identically equal to g(0) as I show in the previous part.
            $endgroup$
            – BenB
            1 hour ago
















          4












          $begingroup$

          $$f(x) = f(x + 0) = g(x cdot 0) = g(0)$$ for all $x$. Thus $f(x)$ is constant and always equal to $g(0)$. Moreover, $$g(0) = f(1 + y) = g(1 cdot y) = g(y)$$ for all $y$. Thus $g$ is also constant and equal to $g(0)$. Thus $f, g$ are the same constant function. All constant functions $f = g = c$ will satisfy the relation. This is all you need.






          share|cite|improve this answer









          $endgroup$









          • 1




            $begingroup$
            Yeah thanks man m looking for this kind of preciseness.
            $endgroup$
            – BORN TO LEARN
            2 hours ago










          • $begingroup$
            Sorry I edited it because I made a mistake in description that g(x)=f(1+y) instead of g(x)=f(1+x).
            $endgroup$
            – BORN TO LEARN
            1 hour ago










          • $begingroup$
            Now I think your proof also needs editing?
            $endgroup$
            – BORN TO LEARN
            1 hour ago










          • $begingroup$
            @BORNTOLEARN where does it need edited? I only used the relation f(x + y) = g(x y).
            $endgroup$
            – BenB
            1 hour ago






          • 1




            $begingroup$
            @BORNTOLEARN because f is identically equal to g(0) as I show in the previous part.
            $endgroup$
            – BenB
            1 hour ago














          4












          4








          4





          $begingroup$

          $$f(x) = f(x + 0) = g(x cdot 0) = g(0)$$ for all $x$. Thus $f(x)$ is constant and always equal to $g(0)$. Moreover, $$g(0) = f(1 + y) = g(1 cdot y) = g(y)$$ for all $y$. Thus $g$ is also constant and equal to $g(0)$. Thus $f, g$ are the same constant function. All constant functions $f = g = c$ will satisfy the relation. This is all you need.






          share|cite|improve this answer









          $endgroup$



          $$f(x) = f(x + 0) = g(x cdot 0) = g(0)$$ for all $x$. Thus $f(x)$ is constant and always equal to $g(0)$. Moreover, $$g(0) = f(1 + y) = g(1 cdot y) = g(y)$$ for all $y$. Thus $g$ is also constant and equal to $g(0)$. Thus $f, g$ are the same constant function. All constant functions $f = g = c$ will satisfy the relation. This is all you need.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered 2 hours ago









          BenBBenB

          46039




          46039








          • 1




            $begingroup$
            Yeah thanks man m looking for this kind of preciseness.
            $endgroup$
            – BORN TO LEARN
            2 hours ago










          • $begingroup$
            Sorry I edited it because I made a mistake in description that g(x)=f(1+y) instead of g(x)=f(1+x).
            $endgroup$
            – BORN TO LEARN
            1 hour ago










          • $begingroup$
            Now I think your proof also needs editing?
            $endgroup$
            – BORN TO LEARN
            1 hour ago










          • $begingroup$
            @BORNTOLEARN where does it need edited? I only used the relation f(x + y) = g(x y).
            $endgroup$
            – BenB
            1 hour ago






          • 1




            $begingroup$
            @BORNTOLEARN because f is identically equal to g(0) as I show in the previous part.
            $endgroup$
            – BenB
            1 hour ago














          • 1




            $begingroup$
            Yeah thanks man m looking for this kind of preciseness.
            $endgroup$
            – BORN TO LEARN
            2 hours ago










          • $begingroup$
            Sorry I edited it because I made a mistake in description that g(x)=f(1+y) instead of g(x)=f(1+x).
            $endgroup$
            – BORN TO LEARN
            1 hour ago










          • $begingroup$
            Now I think your proof also needs editing?
            $endgroup$
            – BORN TO LEARN
            1 hour ago










          • $begingroup$
            @BORNTOLEARN where does it need edited? I only used the relation f(x + y) = g(x y).
            $endgroup$
            – BenB
            1 hour ago






          • 1




            $begingroup$
            @BORNTOLEARN because f is identically equal to g(0) as I show in the previous part.
            $endgroup$
            – BenB
            1 hour ago








          1




          1




          $begingroup$
          Yeah thanks man m looking for this kind of preciseness.
          $endgroup$
          – BORN TO LEARN
          2 hours ago




          $begingroup$
          Yeah thanks man m looking for this kind of preciseness.
          $endgroup$
          – BORN TO LEARN
          2 hours ago












          $begingroup$
          Sorry I edited it because I made a mistake in description that g(x)=f(1+y) instead of g(x)=f(1+x).
          $endgroup$
          – BORN TO LEARN
          1 hour ago




          $begingroup$
          Sorry I edited it because I made a mistake in description that g(x)=f(1+y) instead of g(x)=f(1+x).
          $endgroup$
          – BORN TO LEARN
          1 hour ago












          $begingroup$
          Now I think your proof also needs editing?
          $endgroup$
          – BORN TO LEARN
          1 hour ago




          $begingroup$
          Now I think your proof also needs editing?
          $endgroup$
          – BORN TO LEARN
          1 hour ago












          $begingroup$
          @BORNTOLEARN where does it need edited? I only used the relation f(x + y) = g(x y).
          $endgroup$
          – BenB
          1 hour ago




          $begingroup$
          @BORNTOLEARN where does it need edited? I only used the relation f(x + y) = g(x y).
          $endgroup$
          – BenB
          1 hour ago




          1




          1




          $begingroup$
          @BORNTOLEARN because f is identically equal to g(0) as I show in the previous part.
          $endgroup$
          – BenB
          1 hour ago




          $begingroup$
          @BORNTOLEARN because f is identically equal to g(0) as I show in the previous part.
          $endgroup$
          – BenB
          1 hour ago


















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