Proving by induction of n. Is this correct until this point?prove inequality by induction — Discrete mathProve $25^n>6^n$ using inductionTrying to simplify an expression for an induction proof.Induction on summation inequality stuck on Induction stepProve by Induction: Summation of Factorial (n! * n)Prove that $n! > n^3$ for every integer $n ge 6$ using inductionProving by induction on $n$ that $sum limits_k=1^n (k+1)2^k = n2^n+1 $5. Prove by induction on $n$ that $sumlimits_k=1^n frac kk+1 leq n - frac1n+1$Prove by induction on n that $sumlimits_k=1^n frac k+2k(k+1)2^k+1 = frac12 - frac1(n+1)2^n+1$Prove by induction on n that $sumlimits_k=1^n frac 2^kk leq 2^n$

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Proving by induction of n. Is this correct until this point?


prove inequality by induction — Discrete mathProve $25^n>6^n$ using inductionTrying to simplify an expression for an induction proof.Induction on summation inequality stuck on Induction stepProve by Induction: Summation of Factorial (n! * n)Prove that $n! > n^3$ for every integer $n ge 6$ using inductionProving by induction on $n$ that $sum limits_k=1^n (k+1)2^k = n2^n+1 $5. Prove by induction on $n$ that $sumlimits_k=1^n frac kk+1 leq n - frac1n+1$Prove by induction on n that $sumlimits_k=1^n frac k+2k(k+1)2^k+1 = frac12 - frac1(n+1)2^n+1$Prove by induction on n that $sumlimits_k=1^n frac 2^kk leq 2^n$













4












$begingroup$



$$
sum_k=1^n frac k+2k(k+1)2^k+1 = frac12 - frac1(n+1)2^n+1
$$




Base Case:



I did $n = 1$, so..



LHS-



$$sum_k=1^n frac k+2k(k+1)2^k+1 = frac38$$



RHS-



$$frac12 - frac1(n+1)2^n+1 = frac38$$



so LHS = RHS



Inductive case-



LHS for $n+1$



$$sum_k=1^n+1 frac k+2k(k+1)2^k+1 +frac n+3(n+1)(n+2)2^n+2$$



and then I think that you can use inductive hypothesis to change it to the form of
$$
frac12 - frac1(n+1)2^n+1 +frac n+3(n+1)(n+2)2^n+2
$$



and then I broke up $frac n+3(n+1)(n+2)2^n+2$ into



$$frac2(n+2)-(n+1)(n+1)(n+2)2^n+2$$



$$=$$



$$frac2(n+1)2^n+2 - frac1(n+2)2^n+2$$



$$=$$



$$frac1(n+1)2^n+1 - frac1(n+2)2^n+2$$



then put it back in with the rest of the equation, bringing me to



$$frac12 -frac 1(n+1)2^n+1 +frac1(n+1)2^n+1 - frac1(n+2)2^n+2$$



then



$$frac12 -frac2(n+1)2^n+1 - frac1(n+2)2^n+2$$



and



$$frac12 -frac1(n+1)2^n - frac1(n+2)2^n+2$$



$$frac12 -frac(n+2)2^n+2 - (n+1)2^n(n+1)(n+2)2^2n+2 $$



which I think simplifies down to this after factoring out a $2^n$ from the numerator?



$$frac12 -frac2^n((n+2)2^2 - (n+1))(n+1)(n+2)2^2n+2 $$



canceling out $2^n$



$$frac12 -frac(3n-7)(n+1)(n+2)2^n+2 $$



and I'm stuck, please help!










share|cite|improve this question









$endgroup$
















    4












    $begingroup$



    $$
    sum_k=1^n frac k+2k(k+1)2^k+1 = frac12 - frac1(n+1)2^n+1
    $$




    Base Case:



    I did $n = 1$, so..



    LHS-



    $$sum_k=1^n frac k+2k(k+1)2^k+1 = frac38$$



    RHS-



    $$frac12 - frac1(n+1)2^n+1 = frac38$$



    so LHS = RHS



    Inductive case-



    LHS for $n+1$



    $$sum_k=1^n+1 frac k+2k(k+1)2^k+1 +frac n+3(n+1)(n+2)2^n+2$$



    and then I think that you can use inductive hypothesis to change it to the form of
    $$
    frac12 - frac1(n+1)2^n+1 +frac n+3(n+1)(n+2)2^n+2
    $$



    and then I broke up $frac n+3(n+1)(n+2)2^n+2$ into



    $$frac2(n+2)-(n+1)(n+1)(n+2)2^n+2$$



    $$=$$



    $$frac2(n+1)2^n+2 - frac1(n+2)2^n+2$$



    $$=$$



    $$frac1(n+1)2^n+1 - frac1(n+2)2^n+2$$



    then put it back in with the rest of the equation, bringing me to



    $$frac12 -frac 1(n+1)2^n+1 +frac1(n+1)2^n+1 - frac1(n+2)2^n+2$$



    then



    $$frac12 -frac2(n+1)2^n+1 - frac1(n+2)2^n+2$$



    and



    $$frac12 -frac1(n+1)2^n - frac1(n+2)2^n+2$$



    $$frac12 -frac(n+2)2^n+2 - (n+1)2^n(n+1)(n+2)2^2n+2 $$



    which I think simplifies down to this after factoring out a $2^n$ from the numerator?



    $$frac12 -frac2^n((n+2)2^2 - (n+1))(n+1)(n+2)2^2n+2 $$



    canceling out $2^n$



    $$frac12 -frac(3n-7)(n+1)(n+2)2^n+2 $$



    and I'm stuck, please help!










    share|cite|improve this question









    $endgroup$














      4












      4








      4


      1



      $begingroup$



      $$
      sum_k=1^n frac k+2k(k+1)2^k+1 = frac12 - frac1(n+1)2^n+1
      $$




      Base Case:



      I did $n = 1$, so..



      LHS-



      $$sum_k=1^n frac k+2k(k+1)2^k+1 = frac38$$



      RHS-



      $$frac12 - frac1(n+1)2^n+1 = frac38$$



      so LHS = RHS



      Inductive case-



      LHS for $n+1$



      $$sum_k=1^n+1 frac k+2k(k+1)2^k+1 +frac n+3(n+1)(n+2)2^n+2$$



      and then I think that you can use inductive hypothesis to change it to the form of
      $$
      frac12 - frac1(n+1)2^n+1 +frac n+3(n+1)(n+2)2^n+2
      $$



      and then I broke up $frac n+3(n+1)(n+2)2^n+2$ into



      $$frac2(n+2)-(n+1)(n+1)(n+2)2^n+2$$



      $$=$$



      $$frac2(n+1)2^n+2 - frac1(n+2)2^n+2$$



      $$=$$



      $$frac1(n+1)2^n+1 - frac1(n+2)2^n+2$$



      then put it back in with the rest of the equation, bringing me to



      $$frac12 -frac 1(n+1)2^n+1 +frac1(n+1)2^n+1 - frac1(n+2)2^n+2$$



      then



      $$frac12 -frac2(n+1)2^n+1 - frac1(n+2)2^n+2$$



      and



      $$frac12 -frac1(n+1)2^n - frac1(n+2)2^n+2$$



      $$frac12 -frac(n+2)2^n+2 - (n+1)2^n(n+1)(n+2)2^2n+2 $$



      which I think simplifies down to this after factoring out a $2^n$ from the numerator?



      $$frac12 -frac2^n((n+2)2^2 - (n+1))(n+1)(n+2)2^2n+2 $$



      canceling out $2^n$



      $$frac12 -frac(3n-7)(n+1)(n+2)2^n+2 $$



      and I'm stuck, please help!










      share|cite|improve this question









      $endgroup$





      $$
      sum_k=1^n frac k+2k(k+1)2^k+1 = frac12 - frac1(n+1)2^n+1
      $$




      Base Case:



      I did $n = 1$, so..



      LHS-



      $$sum_k=1^n frac k+2k(k+1)2^k+1 = frac38$$



      RHS-



      $$frac12 - frac1(n+1)2^n+1 = frac38$$



      so LHS = RHS



      Inductive case-



      LHS for $n+1$



      $$sum_k=1^n+1 frac k+2k(k+1)2^k+1 +frac n+3(n+1)(n+2)2^n+2$$



      and then I think that you can use inductive hypothesis to change it to the form of
      $$
      frac12 - frac1(n+1)2^n+1 +frac n+3(n+1)(n+2)2^n+2
      $$



      and then I broke up $frac n+3(n+1)(n+2)2^n+2$ into



      $$frac2(n+2)-(n+1)(n+1)(n+2)2^n+2$$



      $$=$$



      $$frac2(n+1)2^n+2 - frac1(n+2)2^n+2$$



      $$=$$



      $$frac1(n+1)2^n+1 - frac1(n+2)2^n+2$$



      then put it back in with the rest of the equation, bringing me to



      $$frac12 -frac 1(n+1)2^n+1 +frac1(n+1)2^n+1 - frac1(n+2)2^n+2$$



      then



      $$frac12 -frac2(n+1)2^n+1 - frac1(n+2)2^n+2$$



      and



      $$frac12 -frac1(n+1)2^n - frac1(n+2)2^n+2$$



      $$frac12 -frac(n+2)2^n+2 - (n+1)2^n(n+1)(n+2)2^2n+2 $$



      which I think simplifies down to this after factoring out a $2^n$ from the numerator?



      $$frac12 -frac2^n((n+2)2^2 - (n+1))(n+1)(n+2)2^2n+2 $$



      canceling out $2^n$



      $$frac12 -frac(3n-7)(n+1)(n+2)2^n+2 $$



      and I'm stuck, please help!







      discrete-mathematics induction






      share|cite|improve this question













      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked 5 hours ago









      BrownieBrownie

      1927




      1927




















          2 Answers
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          3












          $begingroup$

          Your error is just after the sixth step from the bottom:



          $$frac12 -frac 1(n+1)2^n+1 +frac1(n+1)2^n+1 - frac1(n+2)2^n+2=frac12 -frac1(n+2)2^n+2$$



          Then you are done.



          You accidentally added the two middle terms instead of subtracting.






          share|cite|improve this answer









          $endgroup$




















            2












            $begingroup$

            Using a telescoping sum, we get
            $$
            beginalign
            sum_k=1^nfrack+2k(k+1)2^k+1
            &=sum_k=1^nleft(frac1k2^k-frac1(k+1)2^k+1right)\
            &=sum_k=1^nfrac1k2^k-sum_k=2^n+1frac1k2^k\
            &=frac12-frac1(n+1)2^n+1
            endalign
            $$






            share|cite|improve this answer









            $endgroup$












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              2 Answers
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              2 Answers
              2






              active

              oldest

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              active

              oldest

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              active

              oldest

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              3












              $begingroup$

              Your error is just after the sixth step from the bottom:



              $$frac12 -frac 1(n+1)2^n+1 +frac1(n+1)2^n+1 - frac1(n+2)2^n+2=frac12 -frac1(n+2)2^n+2$$



              Then you are done.



              You accidentally added the two middle terms instead of subtracting.






              share|cite|improve this answer









              $endgroup$

















                3












                $begingroup$

                Your error is just after the sixth step from the bottom:



                $$frac12 -frac 1(n+1)2^n+1 +frac1(n+1)2^n+1 - frac1(n+2)2^n+2=frac12 -frac1(n+2)2^n+2$$



                Then you are done.



                You accidentally added the two middle terms instead of subtracting.






                share|cite|improve this answer









                $endgroup$















                  3












                  3








                  3





                  $begingroup$

                  Your error is just after the sixth step from the bottom:



                  $$frac12 -frac 1(n+1)2^n+1 +frac1(n+1)2^n+1 - frac1(n+2)2^n+2=frac12 -frac1(n+2)2^n+2$$



                  Then you are done.



                  You accidentally added the two middle terms instead of subtracting.






                  share|cite|improve this answer









                  $endgroup$



                  Your error is just after the sixth step from the bottom:



                  $$frac12 -frac 1(n+1)2^n+1 +frac1(n+1)2^n+1 - frac1(n+2)2^n+2=frac12 -frac1(n+2)2^n+2$$



                  Then you are done.



                  You accidentally added the two middle terms instead of subtracting.







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered 4 hours ago









                  John Wayland BalesJohn Wayland Bales

                  15.1k21238




                  15.1k21238





















                      2












                      $begingroup$

                      Using a telescoping sum, we get
                      $$
                      beginalign
                      sum_k=1^nfrack+2k(k+1)2^k+1
                      &=sum_k=1^nleft(frac1k2^k-frac1(k+1)2^k+1right)\
                      &=sum_k=1^nfrac1k2^k-sum_k=2^n+1frac1k2^k\
                      &=frac12-frac1(n+1)2^n+1
                      endalign
                      $$






                      share|cite|improve this answer









                      $endgroup$

















                        2












                        $begingroup$

                        Using a telescoping sum, we get
                        $$
                        beginalign
                        sum_k=1^nfrack+2k(k+1)2^k+1
                        &=sum_k=1^nleft(frac1k2^k-frac1(k+1)2^k+1right)\
                        &=sum_k=1^nfrac1k2^k-sum_k=2^n+1frac1k2^k\
                        &=frac12-frac1(n+1)2^n+1
                        endalign
                        $$






                        share|cite|improve this answer









                        $endgroup$















                          2












                          2








                          2





                          $begingroup$

                          Using a telescoping sum, we get
                          $$
                          beginalign
                          sum_k=1^nfrack+2k(k+1)2^k+1
                          &=sum_k=1^nleft(frac1k2^k-frac1(k+1)2^k+1right)\
                          &=sum_k=1^nfrac1k2^k-sum_k=2^n+1frac1k2^k\
                          &=frac12-frac1(n+1)2^n+1
                          endalign
                          $$






                          share|cite|improve this answer









                          $endgroup$



                          Using a telescoping sum, we get
                          $$
                          beginalign
                          sum_k=1^nfrack+2k(k+1)2^k+1
                          &=sum_k=1^nleft(frac1k2^k-frac1(k+1)2^k+1right)\
                          &=sum_k=1^nfrac1k2^k-sum_k=2^n+1frac1k2^k\
                          &=frac12-frac1(n+1)2^n+1
                          endalign
                          $$







                          share|cite|improve this answer












                          share|cite|improve this answer



                          share|cite|improve this answer










                          answered 3 hours ago









                          robjohnrobjohn

                          270k27312639




                          270k27312639



























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