Differentiate $e^7x^3-frac53$

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up vote
3
down vote

favorite












For this equation I'm using the following property
$$f(x)=e^kx$$
$$f'(x)=ke^kx$$



As well as the product rule
$$f(x)=uv$$
$$f'(x)=u'v+uv'$$



I factorize $x$ on $e$'s exponent and then use the first property to differentiate:
$$e^7x^3-frac53=e^x(7x^2)-frac53=7x^2*e^7x^3-frac53$$



Is his fully differentiated? Or do I have to apply the product rule to $7x^2$? Any other steps I'm missing?







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  • $7x^2$ isn't a constant.
    – poyea
    Aug 24 at 10:42






  • 1




    Ahem. $uv$ is a product, not a quotient.
    – Sean Roberson
    Aug 24 at 10:42










  • @SeanRoberson lmao my bad
    – Pablo
    Aug 24 at 10:43














up vote
3
down vote

favorite












For this equation I'm using the following property
$$f(x)=e^kx$$
$$f'(x)=ke^kx$$



As well as the product rule
$$f(x)=uv$$
$$f'(x)=u'v+uv'$$



I factorize $x$ on $e$'s exponent and then use the first property to differentiate:
$$e^7x^3-frac53=e^x(7x^2)-frac53=7x^2*e^7x^3-frac53$$



Is his fully differentiated? Or do I have to apply the product rule to $7x^2$? Any other steps I'm missing?







share|cite|improve this question






















  • $7x^2$ isn't a constant.
    – poyea
    Aug 24 at 10:42






  • 1




    Ahem. $uv$ is a product, not a quotient.
    – Sean Roberson
    Aug 24 at 10:42










  • @SeanRoberson lmao my bad
    – Pablo
    Aug 24 at 10:43












up vote
3
down vote

favorite









up vote
3
down vote

favorite











For this equation I'm using the following property
$$f(x)=e^kx$$
$$f'(x)=ke^kx$$



As well as the product rule
$$f(x)=uv$$
$$f'(x)=u'v+uv'$$



I factorize $x$ on $e$'s exponent and then use the first property to differentiate:
$$e^7x^3-frac53=e^x(7x^2)-frac53=7x^2*e^7x^3-frac53$$



Is his fully differentiated? Or do I have to apply the product rule to $7x^2$? Any other steps I'm missing?







share|cite|improve this question














For this equation I'm using the following property
$$f(x)=e^kx$$
$$f'(x)=ke^kx$$



As well as the product rule
$$f(x)=uv$$
$$f'(x)=u'v+uv'$$



I factorize $x$ on $e$'s exponent and then use the first property to differentiate:
$$e^7x^3-frac53=e^x(7x^2)-frac53=7x^2*e^7x^3-frac53$$



Is his fully differentiated? Or do I have to apply the product rule to $7x^2$? Any other steps I'm missing?









share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Aug 24 at 10:43

























asked Aug 24 at 10:38









Pablo

33312




33312











  • $7x^2$ isn't a constant.
    – poyea
    Aug 24 at 10:42






  • 1




    Ahem. $uv$ is a product, not a quotient.
    – Sean Roberson
    Aug 24 at 10:42










  • @SeanRoberson lmao my bad
    – Pablo
    Aug 24 at 10:43
















  • $7x^2$ isn't a constant.
    – poyea
    Aug 24 at 10:42






  • 1




    Ahem. $uv$ is a product, not a quotient.
    – Sean Roberson
    Aug 24 at 10:42










  • @SeanRoberson lmao my bad
    – Pablo
    Aug 24 at 10:43















$7x^2$ isn't a constant.
– poyea
Aug 24 at 10:42




$7x^2$ isn't a constant.
– poyea
Aug 24 at 10:42




1




1




Ahem. $uv$ is a product, not a quotient.
– Sean Roberson
Aug 24 at 10:42




Ahem. $uv$ is a product, not a quotient.
– Sean Roberson
Aug 24 at 10:42












@SeanRoberson lmao my bad
– Pablo
Aug 24 at 10:43




@SeanRoberson lmao my bad
– Pablo
Aug 24 at 10:43










3 Answers
3






active

oldest

votes

















up vote
2
down vote



accepted










We need to use chain rule



$$(e^f(x))'=f'(x)e^f(x)$$



with



$$f(x)=7x^3-frac53 implies f'(x)=21x^2$$






share|cite|improve this answer



























    up vote
    3
    down vote













    Remember that when differentiating exponential functions you always get a copy back, multiplied by some other stuff. So we know the derivative contains the term $expleft( 7x^3 - frac53 right)$.



    Now we use the chain. The derivative of the power is $21x^2$ by the usual rules. Here, $frac53$ is a constant and so its derivative vanishes everywhere.



    Thus, the derivative is $21x^2 cdot expleft( 7x^3 - frac53 right)$.



    (Here $exp(x)$ means $e^x$.)






    share|cite|improve this answer



























      up vote
      2
      down vote













      This is not quite right. It's true that
      $$
      fracmathrmdmathrmdxleft[ e^kx right] = ke^kx,,
      $$
      but this is because
      $$
      fracmathrmdmathrmdxleft[ e^f(x) right] = f'(x)cdot e^f(x),.
      $$
      Hence for your question you have
      $$
      fracmathrmdmathrmdxleft[ e^7x^3 - frac53 right] =
      fracmathrmdmathrmdxleft[ 7x^3 - frac53 right]e^7x^3 - frac53,.
      $$
      Can you finish it from here?






      share|cite|improve this answer




















      • got it. i gotta differentiate $7x^3$
        – Pablo
        Aug 24 at 10:45










      • You need to differentiate $7x^3 - frac53$, yes.
        – Bill Wallis
        Aug 24 at 10:48










      Your Answer




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      3 Answers
      3






      active

      oldest

      votes








      3 Answers
      3






      active

      oldest

      votes









      active

      oldest

      votes






      active

      oldest

      votes








      up vote
      2
      down vote



      accepted










      We need to use chain rule



      $$(e^f(x))'=f'(x)e^f(x)$$



      with



      $$f(x)=7x^3-frac53 implies f'(x)=21x^2$$






      share|cite|improve this answer
























        up vote
        2
        down vote



        accepted










        We need to use chain rule



        $$(e^f(x))'=f'(x)e^f(x)$$



        with



        $$f(x)=7x^3-frac53 implies f'(x)=21x^2$$






        share|cite|improve this answer






















          up vote
          2
          down vote



          accepted







          up vote
          2
          down vote



          accepted






          We need to use chain rule



          $$(e^f(x))'=f'(x)e^f(x)$$



          with



          $$f(x)=7x^3-frac53 implies f'(x)=21x^2$$






          share|cite|improve this answer












          We need to use chain rule



          $$(e^f(x))'=f'(x)e^f(x)$$



          with



          $$f(x)=7x^3-frac53 implies f'(x)=21x^2$$







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Aug 24 at 10:42









          gimusi

          69.7k73686




          69.7k73686




















              up vote
              3
              down vote













              Remember that when differentiating exponential functions you always get a copy back, multiplied by some other stuff. So we know the derivative contains the term $expleft( 7x^3 - frac53 right)$.



              Now we use the chain. The derivative of the power is $21x^2$ by the usual rules. Here, $frac53$ is a constant and so its derivative vanishes everywhere.



              Thus, the derivative is $21x^2 cdot expleft( 7x^3 - frac53 right)$.



              (Here $exp(x)$ means $e^x$.)






              share|cite|improve this answer
























                up vote
                3
                down vote













                Remember that when differentiating exponential functions you always get a copy back, multiplied by some other stuff. So we know the derivative contains the term $expleft( 7x^3 - frac53 right)$.



                Now we use the chain. The derivative of the power is $21x^2$ by the usual rules. Here, $frac53$ is a constant and so its derivative vanishes everywhere.



                Thus, the derivative is $21x^2 cdot expleft( 7x^3 - frac53 right)$.



                (Here $exp(x)$ means $e^x$.)






                share|cite|improve this answer






















                  up vote
                  3
                  down vote










                  up vote
                  3
                  down vote









                  Remember that when differentiating exponential functions you always get a copy back, multiplied by some other stuff. So we know the derivative contains the term $expleft( 7x^3 - frac53 right)$.



                  Now we use the chain. The derivative of the power is $21x^2$ by the usual rules. Here, $frac53$ is a constant and so its derivative vanishes everywhere.



                  Thus, the derivative is $21x^2 cdot expleft( 7x^3 - frac53 right)$.



                  (Here $exp(x)$ means $e^x$.)






                  share|cite|improve this answer












                  Remember that when differentiating exponential functions you always get a copy back, multiplied by some other stuff. So we know the derivative contains the term $expleft( 7x^3 - frac53 right)$.



                  Now we use the chain. The derivative of the power is $21x^2$ by the usual rules. Here, $frac53$ is a constant and so its derivative vanishes everywhere.



                  Thus, the derivative is $21x^2 cdot expleft( 7x^3 - frac53 right)$.



                  (Here $exp(x)$ means $e^x$.)







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered Aug 24 at 10:46









                  Sean Roberson

                  5,95231226




                  5,95231226




















                      up vote
                      2
                      down vote













                      This is not quite right. It's true that
                      $$
                      fracmathrmdmathrmdxleft[ e^kx right] = ke^kx,,
                      $$
                      but this is because
                      $$
                      fracmathrmdmathrmdxleft[ e^f(x) right] = f'(x)cdot e^f(x),.
                      $$
                      Hence for your question you have
                      $$
                      fracmathrmdmathrmdxleft[ e^7x^3 - frac53 right] =
                      fracmathrmdmathrmdxleft[ 7x^3 - frac53 right]e^7x^3 - frac53,.
                      $$
                      Can you finish it from here?






                      share|cite|improve this answer




















                      • got it. i gotta differentiate $7x^3$
                        – Pablo
                        Aug 24 at 10:45










                      • You need to differentiate $7x^3 - frac53$, yes.
                        – Bill Wallis
                        Aug 24 at 10:48














                      up vote
                      2
                      down vote













                      This is not quite right. It's true that
                      $$
                      fracmathrmdmathrmdxleft[ e^kx right] = ke^kx,,
                      $$
                      but this is because
                      $$
                      fracmathrmdmathrmdxleft[ e^f(x) right] = f'(x)cdot e^f(x),.
                      $$
                      Hence for your question you have
                      $$
                      fracmathrmdmathrmdxleft[ e^7x^3 - frac53 right] =
                      fracmathrmdmathrmdxleft[ 7x^3 - frac53 right]e^7x^3 - frac53,.
                      $$
                      Can you finish it from here?






                      share|cite|improve this answer




















                      • got it. i gotta differentiate $7x^3$
                        – Pablo
                        Aug 24 at 10:45










                      • You need to differentiate $7x^3 - frac53$, yes.
                        – Bill Wallis
                        Aug 24 at 10:48












                      up vote
                      2
                      down vote










                      up vote
                      2
                      down vote









                      This is not quite right. It's true that
                      $$
                      fracmathrmdmathrmdxleft[ e^kx right] = ke^kx,,
                      $$
                      but this is because
                      $$
                      fracmathrmdmathrmdxleft[ e^f(x) right] = f'(x)cdot e^f(x),.
                      $$
                      Hence for your question you have
                      $$
                      fracmathrmdmathrmdxleft[ e^7x^3 - frac53 right] =
                      fracmathrmdmathrmdxleft[ 7x^3 - frac53 right]e^7x^3 - frac53,.
                      $$
                      Can you finish it from here?






                      share|cite|improve this answer












                      This is not quite right. It's true that
                      $$
                      fracmathrmdmathrmdxleft[ e^kx right] = ke^kx,,
                      $$
                      but this is because
                      $$
                      fracmathrmdmathrmdxleft[ e^f(x) right] = f'(x)cdot e^f(x),.
                      $$
                      Hence for your question you have
                      $$
                      fracmathrmdmathrmdxleft[ e^7x^3 - frac53 right] =
                      fracmathrmdmathrmdxleft[ 7x^3 - frac53 right]e^7x^3 - frac53,.
                      $$
                      Can you finish it from here?







                      share|cite|improve this answer












                      share|cite|improve this answer



                      share|cite|improve this answer










                      answered Aug 24 at 10:43









                      Bill Wallis

                      2,2261826




                      2,2261826











                      • got it. i gotta differentiate $7x^3$
                        – Pablo
                        Aug 24 at 10:45










                      • You need to differentiate $7x^3 - frac53$, yes.
                        – Bill Wallis
                        Aug 24 at 10:48
















                      • got it. i gotta differentiate $7x^3$
                        – Pablo
                        Aug 24 at 10:45










                      • You need to differentiate $7x^3 - frac53$, yes.
                        – Bill Wallis
                        Aug 24 at 10:48















                      got it. i gotta differentiate $7x^3$
                      – Pablo
                      Aug 24 at 10:45




                      got it. i gotta differentiate $7x^3$
                      – Pablo
                      Aug 24 at 10:45












                      You need to differentiate $7x^3 - frac53$, yes.
                      – Bill Wallis
                      Aug 24 at 10:48




                      You need to differentiate $7x^3 - frac53$, yes.
                      – Bill Wallis
                      Aug 24 at 10:48

















                       

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