Simplifying expressions with radical exponents












0












$begingroup$


This is the expression that needs to be simplified:



$frac{(9-x^2)^{1/2} + x^2(9-x^2)^{-1/2}}{9-x^2}$



My first step is to move the negative exponent to the denominator:



$frac{(9-x^2)^{1/2} + x^2}{(9-x^2)(9-x^2)^{1/2}}$



Then multiply the denominator and add the exponents:



$frac{(9-x^2)^{1/2} + x^2}{(9-x^2)^{3/2}}$



I don't know the next steps to reach the given answer of:



$frac{9}{(9-x^2)^{3/2}}$










share|cite|improve this question









$endgroup$












  • $begingroup$
    Your first step is not valid. That can only be done with factors of the whole numerator, not just factors of a term in the numerator.
    $endgroup$
    – MPW
    Dec 29 '18 at 16:23










  • $begingroup$
    $frac{9}{left(9-x^2right)^{3/2}}$
    $endgroup$
    – David G. Stork
    Dec 29 '18 at 16:53
















0












$begingroup$


This is the expression that needs to be simplified:



$frac{(9-x^2)^{1/2} + x^2(9-x^2)^{-1/2}}{9-x^2}$



My first step is to move the negative exponent to the denominator:



$frac{(9-x^2)^{1/2} + x^2}{(9-x^2)(9-x^2)^{1/2}}$



Then multiply the denominator and add the exponents:



$frac{(9-x^2)^{1/2} + x^2}{(9-x^2)^{3/2}}$



I don't know the next steps to reach the given answer of:



$frac{9}{(9-x^2)^{3/2}}$










share|cite|improve this question









$endgroup$












  • $begingroup$
    Your first step is not valid. That can only be done with factors of the whole numerator, not just factors of a term in the numerator.
    $endgroup$
    – MPW
    Dec 29 '18 at 16:23










  • $begingroup$
    $frac{9}{left(9-x^2right)^{3/2}}$
    $endgroup$
    – David G. Stork
    Dec 29 '18 at 16:53














0












0








0





$begingroup$


This is the expression that needs to be simplified:



$frac{(9-x^2)^{1/2} + x^2(9-x^2)^{-1/2}}{9-x^2}$



My first step is to move the negative exponent to the denominator:



$frac{(9-x^2)^{1/2} + x^2}{(9-x^2)(9-x^2)^{1/2}}$



Then multiply the denominator and add the exponents:



$frac{(9-x^2)^{1/2} + x^2}{(9-x^2)^{3/2}}$



I don't know the next steps to reach the given answer of:



$frac{9}{(9-x^2)^{3/2}}$










share|cite|improve this question









$endgroup$




This is the expression that needs to be simplified:



$frac{(9-x^2)^{1/2} + x^2(9-x^2)^{-1/2}}{9-x^2}$



My first step is to move the negative exponent to the denominator:



$frac{(9-x^2)^{1/2} + x^2}{(9-x^2)(9-x^2)^{1/2}}$



Then multiply the denominator and add the exponents:



$frac{(9-x^2)^{1/2} + x^2}{(9-x^2)^{3/2}}$



I don't know the next steps to reach the given answer of:



$frac{9}{(9-x^2)^{3/2}}$







algebra-precalculus radicals






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asked Dec 29 '18 at 16:20









AntoninusAntoninus

33




33












  • $begingroup$
    Your first step is not valid. That can only be done with factors of the whole numerator, not just factors of a term in the numerator.
    $endgroup$
    – MPW
    Dec 29 '18 at 16:23










  • $begingroup$
    $frac{9}{left(9-x^2right)^{3/2}}$
    $endgroup$
    – David G. Stork
    Dec 29 '18 at 16:53


















  • $begingroup$
    Your first step is not valid. That can only be done with factors of the whole numerator, not just factors of a term in the numerator.
    $endgroup$
    – MPW
    Dec 29 '18 at 16:23










  • $begingroup$
    $frac{9}{left(9-x^2right)^{3/2}}$
    $endgroup$
    – David G. Stork
    Dec 29 '18 at 16:53
















$begingroup$
Your first step is not valid. That can only be done with factors of the whole numerator, not just factors of a term in the numerator.
$endgroup$
– MPW
Dec 29 '18 at 16:23




$begingroup$
Your first step is not valid. That can only be done with factors of the whole numerator, not just factors of a term in the numerator.
$endgroup$
– MPW
Dec 29 '18 at 16:23












$begingroup$
$frac{9}{left(9-x^2right)^{3/2}}$
$endgroup$
– David G. Stork
Dec 29 '18 at 16:53




$begingroup$
$frac{9}{left(9-x^2right)^{3/2}}$
$endgroup$
– David G. Stork
Dec 29 '18 at 16:53










3 Answers
3






active

oldest

votes


















0












$begingroup$

Hint: Write $$frac{(9-x^2)^{1/2}}{9-x^2}+frac{x^2(9-x^2)^{-1/2}}{9-x^2}$$ and this is
$$frac{1}{sqrt{9-x^2}}+frac{x^2}{(9-x^2)^{3/2}}$$






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Thank you for the feedback. I understand the right side of this, but I don't understand the left side. You are taking the square-root of the numerator and denominator, but how does the square-root of the numerator simplify to 1?
    $endgroup$
    – Antoninus
    Dec 29 '18 at 16:48










  • $begingroup$
    $$frac{sqrt n}{n} = frac{1}{sqrt n}$$
    $endgroup$
    – KM101
    Dec 29 '18 at 16:51










  • $begingroup$
    Write $$frac{(9-x^2)^{1/2}}{(9-x^2)^{2/2}}$$
    $endgroup$
    – Dr. Sonnhard Graubner
    Dec 29 '18 at 16:52










  • $begingroup$
    Thank you, I've got it now!
    $endgroup$
    – Antoninus
    Dec 29 '18 at 17:11





















0












$begingroup$

Your first step is incorrect.



$$frac{a+b^{-n}}{c} color{red}{neq frac{a}{b^n+c}}$$



You can only bring the negative exponents down when the term is a factor of the whole numerator, not a factor of a single term in the numerator, as in



$$frac{ab^{-n}}{c} = frac{a}{b^nc}$$



Instead, you can make the substitution $u = 9-x^2$:



$$frac{u^{frac{1}{2}} + x^2(u)^{-frac{1}{2}}}{u} = frac{u^{frac{1}{2}}(1+x^2u^{-1})}{u} = frac{1+x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2}{ucdot u^{frac{1}{2}}}$$



Plugging in $u = 9-x^2$ and simplifying gives



$$frac{1}{(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9-x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9}{(9-x^2)^{frac{3}{2}}}$$






share|cite|improve this answer









$endgroup$





















    0












    $begingroup$

    Consider the substitution $z = sqrt{9 - x^2}$ and solve for $x$ and use the $z$ variable.






    share|cite|improve this answer









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      3 Answers
      3






      active

      oldest

      votes








      3 Answers
      3






      active

      oldest

      votes









      active

      oldest

      votes






      active

      oldest

      votes









      0












      $begingroup$

      Hint: Write $$frac{(9-x^2)^{1/2}}{9-x^2}+frac{x^2(9-x^2)^{-1/2}}{9-x^2}$$ and this is
      $$frac{1}{sqrt{9-x^2}}+frac{x^2}{(9-x^2)^{3/2}}$$






      share|cite|improve this answer









      $endgroup$













      • $begingroup$
        Thank you for the feedback. I understand the right side of this, but I don't understand the left side. You are taking the square-root of the numerator and denominator, but how does the square-root of the numerator simplify to 1?
        $endgroup$
        – Antoninus
        Dec 29 '18 at 16:48










      • $begingroup$
        $$frac{sqrt n}{n} = frac{1}{sqrt n}$$
        $endgroup$
        – KM101
        Dec 29 '18 at 16:51










      • $begingroup$
        Write $$frac{(9-x^2)^{1/2}}{(9-x^2)^{2/2}}$$
        $endgroup$
        – Dr. Sonnhard Graubner
        Dec 29 '18 at 16:52










      • $begingroup$
        Thank you, I've got it now!
        $endgroup$
        – Antoninus
        Dec 29 '18 at 17:11


















      0












      $begingroup$

      Hint: Write $$frac{(9-x^2)^{1/2}}{9-x^2}+frac{x^2(9-x^2)^{-1/2}}{9-x^2}$$ and this is
      $$frac{1}{sqrt{9-x^2}}+frac{x^2}{(9-x^2)^{3/2}}$$






      share|cite|improve this answer









      $endgroup$













      • $begingroup$
        Thank you for the feedback. I understand the right side of this, but I don't understand the left side. You are taking the square-root of the numerator and denominator, but how does the square-root of the numerator simplify to 1?
        $endgroup$
        – Antoninus
        Dec 29 '18 at 16:48










      • $begingroup$
        $$frac{sqrt n}{n} = frac{1}{sqrt n}$$
        $endgroup$
        – KM101
        Dec 29 '18 at 16:51










      • $begingroup$
        Write $$frac{(9-x^2)^{1/2}}{(9-x^2)^{2/2}}$$
        $endgroup$
        – Dr. Sonnhard Graubner
        Dec 29 '18 at 16:52










      • $begingroup$
        Thank you, I've got it now!
        $endgroup$
        – Antoninus
        Dec 29 '18 at 17:11
















      0












      0








      0





      $begingroup$

      Hint: Write $$frac{(9-x^2)^{1/2}}{9-x^2}+frac{x^2(9-x^2)^{-1/2}}{9-x^2}$$ and this is
      $$frac{1}{sqrt{9-x^2}}+frac{x^2}{(9-x^2)^{3/2}}$$






      share|cite|improve this answer









      $endgroup$



      Hint: Write $$frac{(9-x^2)^{1/2}}{9-x^2}+frac{x^2(9-x^2)^{-1/2}}{9-x^2}$$ and this is
      $$frac{1}{sqrt{9-x^2}}+frac{x^2}{(9-x^2)^{3/2}}$$







      share|cite|improve this answer












      share|cite|improve this answer



      share|cite|improve this answer










      answered Dec 29 '18 at 16:30









      Dr. Sonnhard GraubnerDr. Sonnhard Graubner

      79.5k42867




      79.5k42867












      • $begingroup$
        Thank you for the feedback. I understand the right side of this, but I don't understand the left side. You are taking the square-root of the numerator and denominator, but how does the square-root of the numerator simplify to 1?
        $endgroup$
        – Antoninus
        Dec 29 '18 at 16:48










      • $begingroup$
        $$frac{sqrt n}{n} = frac{1}{sqrt n}$$
        $endgroup$
        – KM101
        Dec 29 '18 at 16:51










      • $begingroup$
        Write $$frac{(9-x^2)^{1/2}}{(9-x^2)^{2/2}}$$
        $endgroup$
        – Dr. Sonnhard Graubner
        Dec 29 '18 at 16:52










      • $begingroup$
        Thank you, I've got it now!
        $endgroup$
        – Antoninus
        Dec 29 '18 at 17:11




















      • $begingroup$
        Thank you for the feedback. I understand the right side of this, but I don't understand the left side. You are taking the square-root of the numerator and denominator, but how does the square-root of the numerator simplify to 1?
        $endgroup$
        – Antoninus
        Dec 29 '18 at 16:48










      • $begingroup$
        $$frac{sqrt n}{n} = frac{1}{sqrt n}$$
        $endgroup$
        – KM101
        Dec 29 '18 at 16:51










      • $begingroup$
        Write $$frac{(9-x^2)^{1/2}}{(9-x^2)^{2/2}}$$
        $endgroup$
        – Dr. Sonnhard Graubner
        Dec 29 '18 at 16:52










      • $begingroup$
        Thank you, I've got it now!
        $endgroup$
        – Antoninus
        Dec 29 '18 at 17:11


















      $begingroup$
      Thank you for the feedback. I understand the right side of this, but I don't understand the left side. You are taking the square-root of the numerator and denominator, but how does the square-root of the numerator simplify to 1?
      $endgroup$
      – Antoninus
      Dec 29 '18 at 16:48




      $begingroup$
      Thank you for the feedback. I understand the right side of this, but I don't understand the left side. You are taking the square-root of the numerator and denominator, but how does the square-root of the numerator simplify to 1?
      $endgroup$
      – Antoninus
      Dec 29 '18 at 16:48












      $begingroup$
      $$frac{sqrt n}{n} = frac{1}{sqrt n}$$
      $endgroup$
      – KM101
      Dec 29 '18 at 16:51




      $begingroup$
      $$frac{sqrt n}{n} = frac{1}{sqrt n}$$
      $endgroup$
      – KM101
      Dec 29 '18 at 16:51












      $begingroup$
      Write $$frac{(9-x^2)^{1/2}}{(9-x^2)^{2/2}}$$
      $endgroup$
      – Dr. Sonnhard Graubner
      Dec 29 '18 at 16:52




      $begingroup$
      Write $$frac{(9-x^2)^{1/2}}{(9-x^2)^{2/2}}$$
      $endgroup$
      – Dr. Sonnhard Graubner
      Dec 29 '18 at 16:52












      $begingroup$
      Thank you, I've got it now!
      $endgroup$
      – Antoninus
      Dec 29 '18 at 17:11






      $begingroup$
      Thank you, I've got it now!
      $endgroup$
      – Antoninus
      Dec 29 '18 at 17:11













      0












      $begingroup$

      Your first step is incorrect.



      $$frac{a+b^{-n}}{c} color{red}{neq frac{a}{b^n+c}}$$



      You can only bring the negative exponents down when the term is a factor of the whole numerator, not a factor of a single term in the numerator, as in



      $$frac{ab^{-n}}{c} = frac{a}{b^nc}$$



      Instead, you can make the substitution $u = 9-x^2$:



      $$frac{u^{frac{1}{2}} + x^2(u)^{-frac{1}{2}}}{u} = frac{u^{frac{1}{2}}(1+x^2u^{-1})}{u} = frac{1+x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2}{ucdot u^{frac{1}{2}}}$$



      Plugging in $u = 9-x^2$ and simplifying gives



      $$frac{1}{(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9-x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9}{(9-x^2)^{frac{3}{2}}}$$






      share|cite|improve this answer









      $endgroup$


















        0












        $begingroup$

        Your first step is incorrect.



        $$frac{a+b^{-n}}{c} color{red}{neq frac{a}{b^n+c}}$$



        You can only bring the negative exponents down when the term is a factor of the whole numerator, not a factor of a single term in the numerator, as in



        $$frac{ab^{-n}}{c} = frac{a}{b^nc}$$



        Instead, you can make the substitution $u = 9-x^2$:



        $$frac{u^{frac{1}{2}} + x^2(u)^{-frac{1}{2}}}{u} = frac{u^{frac{1}{2}}(1+x^2u^{-1})}{u} = frac{1+x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2}{ucdot u^{frac{1}{2}}}$$



        Plugging in $u = 9-x^2$ and simplifying gives



        $$frac{1}{(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9-x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9}{(9-x^2)^{frac{3}{2}}}$$






        share|cite|improve this answer









        $endgroup$
















          0












          0








          0





          $begingroup$

          Your first step is incorrect.



          $$frac{a+b^{-n}}{c} color{red}{neq frac{a}{b^n+c}}$$



          You can only bring the negative exponents down when the term is a factor of the whole numerator, not a factor of a single term in the numerator, as in



          $$frac{ab^{-n}}{c} = frac{a}{b^nc}$$



          Instead, you can make the substitution $u = 9-x^2$:



          $$frac{u^{frac{1}{2}} + x^2(u)^{-frac{1}{2}}}{u} = frac{u^{frac{1}{2}}(1+x^2u^{-1})}{u} = frac{1+x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2}{ucdot u^{frac{1}{2}}}$$



          Plugging in $u = 9-x^2$ and simplifying gives



          $$frac{1}{(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9-x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9}{(9-x^2)^{frac{3}{2}}}$$






          share|cite|improve this answer









          $endgroup$



          Your first step is incorrect.



          $$frac{a+b^{-n}}{c} color{red}{neq frac{a}{b^n+c}}$$



          You can only bring the negative exponents down when the term is a factor of the whole numerator, not a factor of a single term in the numerator, as in



          $$frac{ab^{-n}}{c} = frac{a}{b^nc}$$



          Instead, you can make the substitution $u = 9-x^2$:



          $$frac{u^{frac{1}{2}} + x^2(u)^{-frac{1}{2}}}{u} = frac{u^{frac{1}{2}}(1+x^2u^{-1})}{u} = frac{1+x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2u^{-1}}{u^{frac{1}{2}}} = frac{1}{u^{frac{1}{2}}}+frac{x^2}{ucdot u^{frac{1}{2}}}$$



          Plugging in $u = 9-x^2$ and simplifying gives



          $$frac{1}{(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9-x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}}+frac{x^2}{(9-x^2)(9-x^2)^{frac{1}{2}}} = frac{9}{(9-x^2)^{frac{3}{2}}}$$







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Dec 29 '18 at 16:49









          KM101KM101

          6,0861525




          6,0861525























              0












              $begingroup$

              Consider the substitution $z = sqrt{9 - x^2}$ and solve for $x$ and use the $z$ variable.






              share|cite|improve this answer









              $endgroup$


















                0












                $begingroup$

                Consider the substitution $z = sqrt{9 - x^2}$ and solve for $x$ and use the $z$ variable.






                share|cite|improve this answer









                $endgroup$
















                  0












                  0








                  0





                  $begingroup$

                  Consider the substitution $z = sqrt{9 - x^2}$ and solve for $x$ and use the $z$ variable.






                  share|cite|improve this answer









                  $endgroup$



                  Consider the substitution $z = sqrt{9 - x^2}$ and solve for $x$ and use the $z$ variable.







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered Dec 29 '18 at 19:12









                  Lorenz H MenkeLorenz H Menke

                  9611




                  9611






























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