Solving non-homogeneous recurrence relationships with exponents











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Find all solutions of the recurrence relation $a_n = 2a_{n-1} + 2n^2$.



I am having trouble with coming up with a guess for $2n^2$. Would it just be $an^2 + bn + c$?



I feel like there's an easier way based on ways to solve other recurrances.










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    up vote
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    down vote

    favorite












    Find all solutions of the recurrence relation $a_n = 2a_{n-1} + 2n^2$.



    I am having trouble with coming up with a guess for $2n^2$. Would it just be $an^2 + bn + c$?



    I feel like there's an easier way based on ways to solve other recurrances.










    share|cite|improve this question
























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      Find all solutions of the recurrence relation $a_n = 2a_{n-1} + 2n^2$.



      I am having trouble with coming up with a guess for $2n^2$. Would it just be $an^2 + bn + c$?



      I feel like there's an easier way based on ways to solve other recurrances.










      share|cite|improve this question













      Find all solutions of the recurrence relation $a_n = 2a_{n-1} + 2n^2$.



      I am having trouble with coming up with a guess for $2n^2$. Would it just be $an^2 + bn + c$?



      I feel like there's an easier way based on ways to solve other recurrances.







      recurrence-relations






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      asked Nov 25 at 21:24









      Jersey Fonseca

      356




      356






















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          If you're familiar with the $Z$-transform you can find a systematic way to solve these kind of relations. Otherwise, a guess of the form



          $$
          a_n = alpha + beta n + gamma n^2 + delta 2^{n}
          $$



          The actual solution is



          $$
          a_n = left(frac{a_1}{2} + 11right) 2^n - 2 n^2 - 8 n -12
          $$






          share|cite|improve this answer





















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            1 Answer
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            active

            oldest

            votes








            1 Answer
            1






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes








            up vote
            0
            down vote













            If you're familiar with the $Z$-transform you can find a systematic way to solve these kind of relations. Otherwise, a guess of the form



            $$
            a_n = alpha + beta n + gamma n^2 + delta 2^{n}
            $$



            The actual solution is



            $$
            a_n = left(frac{a_1}{2} + 11right) 2^n - 2 n^2 - 8 n -12
            $$






            share|cite|improve this answer

























              up vote
              0
              down vote













              If you're familiar with the $Z$-transform you can find a systematic way to solve these kind of relations. Otherwise, a guess of the form



              $$
              a_n = alpha + beta n + gamma n^2 + delta 2^{n}
              $$



              The actual solution is



              $$
              a_n = left(frac{a_1}{2} + 11right) 2^n - 2 n^2 - 8 n -12
              $$






              share|cite|improve this answer























                up vote
                0
                down vote










                up vote
                0
                down vote









                If you're familiar with the $Z$-transform you can find a systematic way to solve these kind of relations. Otherwise, a guess of the form



                $$
                a_n = alpha + beta n + gamma n^2 + delta 2^{n}
                $$



                The actual solution is



                $$
                a_n = left(frac{a_1}{2} + 11right) 2^n - 2 n^2 - 8 n -12
                $$






                share|cite|improve this answer












                If you're familiar with the $Z$-transform you can find a systematic way to solve these kind of relations. Otherwise, a guess of the form



                $$
                a_n = alpha + beta n + gamma n^2 + delta 2^{n}
                $$



                The actual solution is



                $$
                a_n = left(frac{a_1}{2} + 11right) 2^n - 2 n^2 - 8 n -12
                $$







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Nov 25 at 22:51









                caverac

                12.5k21027




                12.5k21027






























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