Finding remainder when unknown $f(x)$ is divided to $g(x)$












4












$begingroup$


When $f(x)$ is divided by $x - 2$ and $x + 3$, the remainders are 5 and -1, respectively. Find the remainder when $f(x)$ is divided by $x^2 + x - 6$



My method:
Since $x - 2$ and $x + 3$ are linears, dividing by quadratic will leave linear remainders.



Using the remainder theorem:
$$ f(x) = g(x) q(x) + r(x) $$
Where $g(x)$ is a divisor, $q(x)$ is a remainder, and $r(x)$ is a remainder



I let $ax + b$ here be the remainder.
So:



begin{align}
f(x) &= g(x) (x - 2)(x + 3) + ax + b\
f(2) &= g(2) (0)(5) + 2a+ b\
f(-3) &= g(-3) (-5)(0) - 3a + b\
\
&5 = 2a + b\
&-1 = -3a + b\
\
&...\
\
&a = frac{6}{5}, b = frac{13}{5}
\
end{align}



Then the remainder is $ax + b = frac{6}{5}x + frac{13}{5} $



Is it possible to find the $f(x)$ out of remainders?










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$endgroup$

















    4












    $begingroup$


    When $f(x)$ is divided by $x - 2$ and $x + 3$, the remainders are 5 and -1, respectively. Find the remainder when $f(x)$ is divided by $x^2 + x - 6$



    My method:
    Since $x - 2$ and $x + 3$ are linears, dividing by quadratic will leave linear remainders.



    Using the remainder theorem:
    $$ f(x) = g(x) q(x) + r(x) $$
    Where $g(x)$ is a divisor, $q(x)$ is a remainder, and $r(x)$ is a remainder



    I let $ax + b$ here be the remainder.
    So:



    begin{align}
    f(x) &= g(x) (x - 2)(x + 3) + ax + b\
    f(2) &= g(2) (0)(5) + 2a+ b\
    f(-3) &= g(-3) (-5)(0) - 3a + b\
    \
    &5 = 2a + b\
    &-1 = -3a + b\
    \
    &...\
    \
    &a = frac{6}{5}, b = frac{13}{5}
    \
    end{align}



    Then the remainder is $ax + b = frac{6}{5}x + frac{13}{5} $



    Is it possible to find the $f(x)$ out of remainders?










    share|cite|improve this question











    $endgroup$















      4












      4








      4





      $begingroup$


      When $f(x)$ is divided by $x - 2$ and $x + 3$, the remainders are 5 and -1, respectively. Find the remainder when $f(x)$ is divided by $x^2 + x - 6$



      My method:
      Since $x - 2$ and $x + 3$ are linears, dividing by quadratic will leave linear remainders.



      Using the remainder theorem:
      $$ f(x) = g(x) q(x) + r(x) $$
      Where $g(x)$ is a divisor, $q(x)$ is a remainder, and $r(x)$ is a remainder



      I let $ax + b$ here be the remainder.
      So:



      begin{align}
      f(x) &= g(x) (x - 2)(x + 3) + ax + b\
      f(2) &= g(2) (0)(5) + 2a+ b\
      f(-3) &= g(-3) (-5)(0) - 3a + b\
      \
      &5 = 2a + b\
      &-1 = -3a + b\
      \
      &...\
      \
      &a = frac{6}{5}, b = frac{13}{5}
      \
      end{align}



      Then the remainder is $ax + b = frac{6}{5}x + frac{13}{5} $



      Is it possible to find the $f(x)$ out of remainders?










      share|cite|improve this question











      $endgroup$




      When $f(x)$ is divided by $x - 2$ and $x + 3$, the remainders are 5 and -1, respectively. Find the remainder when $f(x)$ is divided by $x^2 + x - 6$



      My method:
      Since $x - 2$ and $x + 3$ are linears, dividing by quadratic will leave linear remainders.



      Using the remainder theorem:
      $$ f(x) = g(x) q(x) + r(x) $$
      Where $g(x)$ is a divisor, $q(x)$ is a remainder, and $r(x)$ is a remainder



      I let $ax + b$ here be the remainder.
      So:



      begin{align}
      f(x) &= g(x) (x - 2)(x + 3) + ax + b\
      f(2) &= g(2) (0)(5) + 2a+ b\
      f(-3) &= g(-3) (-5)(0) - 3a + b\
      \
      &5 = 2a + b\
      &-1 = -3a + b\
      \
      &...\
      \
      &a = frac{6}{5}, b = frac{13}{5}
      \
      end{align}



      Then the remainder is $ax + b = frac{6}{5}x + frac{13}{5} $



      Is it possible to find the $f(x)$ out of remainders?







      proof-verification polynomials roots






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      edited Jan 20 at 9:33







      MMJM

















      asked Jan 20 at 8:51









      MMJMMMJM

      3351111




      3351111






















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          $begingroup$

          No, there are infinite $f(x)$ which satisfy the given conditions:
          $$f(x)=q(x)(x^2 + x - 6)+frac{6}{5}x + frac{13}{5}$$
          with any polynomial $q(x)$.






          share|cite|improve this answer











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            $begingroup$

            No, there are infinite $f(x)$ which satisfy the given conditions:
            $$f(x)=q(x)(x^2 + x - 6)+frac{6}{5}x + frac{13}{5}$$
            with any polynomial $q(x)$.






            share|cite|improve this answer











            $endgroup$


















              3












              $begingroup$

              No, there are infinite $f(x)$ which satisfy the given conditions:
              $$f(x)=q(x)(x^2 + x - 6)+frac{6}{5}x + frac{13}{5}$$
              with any polynomial $q(x)$.






              share|cite|improve this answer











              $endgroup$
















                3












                3








                3





                $begingroup$

                No, there are infinite $f(x)$ which satisfy the given conditions:
                $$f(x)=q(x)(x^2 + x - 6)+frac{6}{5}x + frac{13}{5}$$
                with any polynomial $q(x)$.






                share|cite|improve this answer











                $endgroup$



                No, there are infinite $f(x)$ which satisfy the given conditions:
                $$f(x)=q(x)(x^2 + x - 6)+frac{6}{5}x + frac{13}{5}$$
                with any polynomial $q(x)$.







                share|cite|improve this answer














                share|cite|improve this answer



                share|cite|improve this answer








                edited Jan 20 at 9:05

























                answered Jan 20 at 8:59









                Robert ZRobert Z

                98.3k1067139




                98.3k1067139






























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