Prove that there is a basis for the $n$th degree polynomial vector space consisting $only$ of $n$th degree polynomials.

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I tried looking around for an answer to this question, but I couldn't find anything specific enough. I'm thinking I need to use either Cartesian products or subspace sums to produce such a vector space, however I'm still fuzzy on how to actually implement it.



Any help would be great!










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  • What is the $n$-th degree polynomial vector space? Is that the vector space of polynomials (coefficients in some field) whose degree is at most $n$?
    – Dave
    Sep 10 at 18:56










  • Yes, that's my understanding. My text uses the notation 𝔽[$x$;$n$], without any explanation as to how it should be read, unfortunately.
    – Silverwing171
    Sep 10 at 19:00










  • Hint: if $v_1,v_2,dots,v_n$ is a basis for a vector space, then so is $v_1+v_n,v_2,dots,v_n$.
    – amd
    Sep 10 at 22:58














up vote
1
down vote

favorite












I tried looking around for an answer to this question, but I couldn't find anything specific enough. I'm thinking I need to use either Cartesian products or subspace sums to produce such a vector space, however I'm still fuzzy on how to actually implement it.



Any help would be great!










share|cite|improve this question





















  • What is the $n$-th degree polynomial vector space? Is that the vector space of polynomials (coefficients in some field) whose degree is at most $n$?
    – Dave
    Sep 10 at 18:56










  • Yes, that's my understanding. My text uses the notation 𝔽[$x$;$n$], without any explanation as to how it should be read, unfortunately.
    – Silverwing171
    Sep 10 at 19:00










  • Hint: if $v_1,v_2,dots,v_n$ is a basis for a vector space, then so is $v_1+v_n,v_2,dots,v_n$.
    – amd
    Sep 10 at 22:58












up vote
1
down vote

favorite









up vote
1
down vote

favorite











I tried looking around for an answer to this question, but I couldn't find anything specific enough. I'm thinking I need to use either Cartesian products or subspace sums to produce such a vector space, however I'm still fuzzy on how to actually implement it.



Any help would be great!










share|cite|improve this question













I tried looking around for an answer to this question, but I couldn't find anything specific enough. I'm thinking I need to use either Cartesian products or subspace sums to produce such a vector space, however I'm still fuzzy on how to actually implement it.



Any help would be great!







linear-algebra polynomials vector-spaces






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asked Sep 10 at 18:53









Silverwing171

82




82











  • What is the $n$-th degree polynomial vector space? Is that the vector space of polynomials (coefficients in some field) whose degree is at most $n$?
    – Dave
    Sep 10 at 18:56










  • Yes, that's my understanding. My text uses the notation 𝔽[$x$;$n$], without any explanation as to how it should be read, unfortunately.
    – Silverwing171
    Sep 10 at 19:00










  • Hint: if $v_1,v_2,dots,v_n$ is a basis for a vector space, then so is $v_1+v_n,v_2,dots,v_n$.
    – amd
    Sep 10 at 22:58
















  • What is the $n$-th degree polynomial vector space? Is that the vector space of polynomials (coefficients in some field) whose degree is at most $n$?
    – Dave
    Sep 10 at 18:56










  • Yes, that's my understanding. My text uses the notation 𝔽[$x$;$n$], without any explanation as to how it should be read, unfortunately.
    – Silverwing171
    Sep 10 at 19:00










  • Hint: if $v_1,v_2,dots,v_n$ is a basis for a vector space, then so is $v_1+v_n,v_2,dots,v_n$.
    – amd
    Sep 10 at 22:58















What is the $n$-th degree polynomial vector space? Is that the vector space of polynomials (coefficients in some field) whose degree is at most $n$?
– Dave
Sep 10 at 18:56




What is the $n$-th degree polynomial vector space? Is that the vector space of polynomials (coefficients in some field) whose degree is at most $n$?
– Dave
Sep 10 at 18:56












Yes, that's my understanding. My text uses the notation 𝔽[$x$;$n$], without any explanation as to how it should be read, unfortunately.
– Silverwing171
Sep 10 at 19:00




Yes, that's my understanding. My text uses the notation 𝔽[$x$;$n$], without any explanation as to how it should be read, unfortunately.
– Silverwing171
Sep 10 at 19:00












Hint: if $v_1,v_2,dots,v_n$ is a basis for a vector space, then so is $v_1+v_n,v_2,dots,v_n$.
– amd
Sep 10 at 22:58




Hint: if $v_1,v_2,dots,v_n$ is a basis for a vector space, then so is $v_1+v_n,v_2,dots,v_n$.
– amd
Sep 10 at 22:58










2 Answers
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Hint:



We know that $1, x, x^2, ldots, x^n$ is a basis for your space. But then $$1+x^n, x+x^n, x^2+x^n, ldots, 2x^n$$



is also a basis for your space.






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    Pick any basis $f_1, ldots, f_n, f_n+1$. At least one of these polynomials must have degree exactly $n$, otherwise $x^n$ would not be in the generated subspace.
    WLOG $deg f_1 =n$.
    If some of the other basis vectors have smaller degree, add $f_1$ to them (and only to those with degree strictly less than $n$).
    That yields a solution you were looking for.






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      2 Answers
      2






      active

      oldest

      votes








      2 Answers
      2






      active

      oldest

      votes









      active

      oldest

      votes






      active

      oldest

      votes








      up vote
      0
      down vote



      accepted










      Hint:



      We know that $1, x, x^2, ldots, x^n$ is a basis for your space. But then $$1+x^n, x+x^n, x^2+x^n, ldots, 2x^n$$



      is also a basis for your space.






      share|cite|improve this answer
























        up vote
        0
        down vote



        accepted










        Hint:



        We know that $1, x, x^2, ldots, x^n$ is a basis for your space. But then $$1+x^n, x+x^n, x^2+x^n, ldots, 2x^n$$



        is also a basis for your space.






        share|cite|improve this answer






















          up vote
          0
          down vote



          accepted







          up vote
          0
          down vote



          accepted






          Hint:



          We know that $1, x, x^2, ldots, x^n$ is a basis for your space. But then $$1+x^n, x+x^n, x^2+x^n, ldots, 2x^n$$



          is also a basis for your space.






          share|cite|improve this answer












          Hint:



          We know that $1, x, x^2, ldots, x^n$ is a basis for your space. But then $$1+x^n, x+x^n, x^2+x^n, ldots, 2x^n$$



          is also a basis for your space.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Sep 10 at 19:44









          mechanodroid

          24.7k62245




          24.7k62245




















              up vote
              0
              down vote













              Pick any basis $f_1, ldots, f_n, f_n+1$. At least one of these polynomials must have degree exactly $n$, otherwise $x^n$ would not be in the generated subspace.
              WLOG $deg f_1 =n$.
              If some of the other basis vectors have smaller degree, add $f_1$ to them (and only to those with degree strictly less than $n$).
              That yields a solution you were looking for.






              share|cite|improve this answer
























                up vote
                0
                down vote













                Pick any basis $f_1, ldots, f_n, f_n+1$. At least one of these polynomials must have degree exactly $n$, otherwise $x^n$ would not be in the generated subspace.
                WLOG $deg f_1 =n$.
                If some of the other basis vectors have smaller degree, add $f_1$ to them (and only to those with degree strictly less than $n$).
                That yields a solution you were looking for.






                share|cite|improve this answer






















                  up vote
                  0
                  down vote










                  up vote
                  0
                  down vote









                  Pick any basis $f_1, ldots, f_n, f_n+1$. At least one of these polynomials must have degree exactly $n$, otherwise $x^n$ would not be in the generated subspace.
                  WLOG $deg f_1 =n$.
                  If some of the other basis vectors have smaller degree, add $f_1$ to them (and only to those with degree strictly less than $n$).
                  That yields a solution you were looking for.






                  share|cite|improve this answer












                  Pick any basis $f_1, ldots, f_n, f_n+1$. At least one of these polynomials must have degree exactly $n$, otherwise $x^n$ would not be in the generated subspace.
                  WLOG $deg f_1 =n$.
                  If some of the other basis vectors have smaller degree, add $f_1$ to them (and only to those with degree strictly less than $n$).
                  That yields a solution you were looking for.







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered Sep 10 at 19:09









                  A. Pongrácz

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