Finding the dimension of $U={p(x) in mathbb{R}_3[x]text{ } |text{ } p(a) = 0}$.












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Let $a in mathbb{R}$ and $U = {p(x) in mathbb{R}_3[x]text{ } |text{ } p(a) = 0}$. How do I find $dim(U)$?










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    $begingroup$


    Let $a in mathbb{R}$ and $U = {p(x) in mathbb{R}_3[x]text{ } |text{ } p(a) = 0}$. How do I find $dim(U)$?










    share|cite|improve this question











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      1








      1





      $begingroup$


      Let $a in mathbb{R}$ and $U = {p(x) in mathbb{R}_3[x]text{ } |text{ } p(a) = 0}$. How do I find $dim(U)$?










      share|cite|improve this question











      $endgroup$




      Let $a in mathbb{R}$ and $U = {p(x) in mathbb{R}_3[x]text{ } |text{ } p(a) = 0}$. How do I find $dim(U)$?







      linear-algebra






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      edited Dec 23 '18 at 16:47









      projectilemotion

      11.4k62141




      11.4k62141










      asked Dec 23 '18 at 16:38









      Yuki1112Yuki1112

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          $begingroup$

          Let $p(x)=a_0+a_1x+a_2x^2+a_3x^3in U,a_iinBbb R$



          $p(a)=0implies a_0+a_1a+a_2a^2+a_3a^3=0$



          Substitute for $a_0$ in $p(x)$,



          $p(x)=-(a_1a+a_2a^2+a_3a^3)+a_1x+a_2x^2+a_3x^3=a_1(x-a)+a_2(x^2-a^2)+a_3(x^3-a^3)$



          which is a linear combination of $3$ linearly independent vectors of $Bbb R_3[x]$, giving the dimension as $3$.






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            $begingroup$

            Let $p(x)=a_0+a_1x+a_2x^2+a_3x^3in U,a_iinBbb R$



            $p(a)=0implies a_0+a_1a+a_2a^2+a_3a^3=0$



            Substitute for $a_0$ in $p(x)$,



            $p(x)=-(a_1a+a_2a^2+a_3a^3)+a_1x+a_2x^2+a_3x^3=a_1(x-a)+a_2(x^2-a^2)+a_3(x^3-a^3)$



            which is a linear combination of $3$ linearly independent vectors of $Bbb R_3[x]$, giving the dimension as $3$.






            share|cite|improve this answer









            $endgroup$


















              1












              $begingroup$

              Let $p(x)=a_0+a_1x+a_2x^2+a_3x^3in U,a_iinBbb R$



              $p(a)=0implies a_0+a_1a+a_2a^2+a_3a^3=0$



              Substitute for $a_0$ in $p(x)$,



              $p(x)=-(a_1a+a_2a^2+a_3a^3)+a_1x+a_2x^2+a_3x^3=a_1(x-a)+a_2(x^2-a^2)+a_3(x^3-a^3)$



              which is a linear combination of $3$ linearly independent vectors of $Bbb R_3[x]$, giving the dimension as $3$.






              share|cite|improve this answer









              $endgroup$
















                1












                1








                1





                $begingroup$

                Let $p(x)=a_0+a_1x+a_2x^2+a_3x^3in U,a_iinBbb R$



                $p(a)=0implies a_0+a_1a+a_2a^2+a_3a^3=0$



                Substitute for $a_0$ in $p(x)$,



                $p(x)=-(a_1a+a_2a^2+a_3a^3)+a_1x+a_2x^2+a_3x^3=a_1(x-a)+a_2(x^2-a^2)+a_3(x^3-a^3)$



                which is a linear combination of $3$ linearly independent vectors of $Bbb R_3[x]$, giving the dimension as $3$.






                share|cite|improve this answer









                $endgroup$



                Let $p(x)=a_0+a_1x+a_2x^2+a_3x^3in U,a_iinBbb R$



                $p(a)=0implies a_0+a_1a+a_2a^2+a_3a^3=0$



                Substitute for $a_0$ in $p(x)$,



                $p(x)=-(a_1a+a_2a^2+a_3a^3)+a_1x+a_2x^2+a_3x^3=a_1(x-a)+a_2(x^2-a^2)+a_3(x^3-a^3)$



                which is a linear combination of $3$ linearly independent vectors of $Bbb R_3[x]$, giving the dimension as $3$.







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Dec 23 '18 at 18:29









                Shubham JohriShubham Johri

                5,204718




                5,204718






























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