calculate limit without L'Hospital's Rules












0












$begingroup$


I'm struggling with this limit. We did not learn L'Hospital's Rule, Taylor expansions, etc. yet. Should be solvable with plain old limit arithmetic:



$lim_limits{x to 1} (frac{3}{1-sqrt{x}}-frac{2}{1-sqrt[3]{x}})$



I tried combining the fractions with the common denominator, I tried multiplying each one by the conjugates, substituting different values as t.



Still haven't had my breakthrough yet.



Please help, thanks










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  • $begingroup$
    See math.stackexchange.com/questions/529961/…
    $endgroup$
    – lab bhattacharjee
    Jan 24 at 11:56
















0












$begingroup$


I'm struggling with this limit. We did not learn L'Hospital's Rule, Taylor expansions, etc. yet. Should be solvable with plain old limit arithmetic:



$lim_limits{x to 1} (frac{3}{1-sqrt{x}}-frac{2}{1-sqrt[3]{x}})$



I tried combining the fractions with the common denominator, I tried multiplying each one by the conjugates, substituting different values as t.



Still haven't had my breakthrough yet.



Please help, thanks










share|cite|improve this question











$endgroup$












  • $begingroup$
    See math.stackexchange.com/questions/529961/…
    $endgroup$
    – lab bhattacharjee
    Jan 24 at 11:56














0












0








0





$begingroup$


I'm struggling with this limit. We did not learn L'Hospital's Rule, Taylor expansions, etc. yet. Should be solvable with plain old limit arithmetic:



$lim_limits{x to 1} (frac{3}{1-sqrt{x}}-frac{2}{1-sqrt[3]{x}})$



I tried combining the fractions with the common denominator, I tried multiplying each one by the conjugates, substituting different values as t.



Still haven't had my breakthrough yet.



Please help, thanks










share|cite|improve this question











$endgroup$




I'm struggling with this limit. We did not learn L'Hospital's Rule, Taylor expansions, etc. yet. Should be solvable with plain old limit arithmetic:



$lim_limits{x to 1} (frac{3}{1-sqrt{x}}-frac{2}{1-sqrt[3]{x}})$



I tried combining the fractions with the common denominator, I tried multiplying each one by the conjugates, substituting different values as t.



Still haven't had my breakthrough yet.



Please help, thanks







limits limits-without-lhopital






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edited Jan 24 at 10:58









Bernard

122k740116




122k740116










asked Jan 24 at 10:38









ikoikoiaikoikoia

1399




1399












  • $begingroup$
    See math.stackexchange.com/questions/529961/…
    $endgroup$
    – lab bhattacharjee
    Jan 24 at 11:56


















  • $begingroup$
    See math.stackexchange.com/questions/529961/…
    $endgroup$
    – lab bhattacharjee
    Jan 24 at 11:56
















$begingroup$
See math.stackexchange.com/questions/529961/…
$endgroup$
– lab bhattacharjee
Jan 24 at 11:56




$begingroup$
See math.stackexchange.com/questions/529961/…
$endgroup$
– lab bhattacharjee
Jan 24 at 11:56










1 Answer
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$begingroup$

Hint: We can substitute $x=t^6$ to obtain
$$
lim_{tto 1}frac{3}{1-t^3}-frac{2}{1-t^2}=lim_{tto 1}frac{1}{1-t}left(frac{3}{t^2+t+1}-frac{2}{1+t}right).
$$






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    1 Answer
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    1 Answer
    1






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    4












    $begingroup$

    Hint: We can substitute $x=t^6$ to obtain
    $$
    lim_{tto 1}frac{3}{1-t^3}-frac{2}{1-t^2}=lim_{tto 1}frac{1}{1-t}left(frac{3}{t^2+t+1}-frac{2}{1+t}right).
    $$






    share|cite|improve this answer









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      4












      $begingroup$

      Hint: We can substitute $x=t^6$ to obtain
      $$
      lim_{tto 1}frac{3}{1-t^3}-frac{2}{1-t^2}=lim_{tto 1}frac{1}{1-t}left(frac{3}{t^2+t+1}-frac{2}{1+t}right).
      $$






      share|cite|improve this answer









      $endgroup$
















        4












        4








        4





        $begingroup$

        Hint: We can substitute $x=t^6$ to obtain
        $$
        lim_{tto 1}frac{3}{1-t^3}-frac{2}{1-t^2}=lim_{tto 1}frac{1}{1-t}left(frac{3}{t^2+t+1}-frac{2}{1+t}right).
        $$






        share|cite|improve this answer









        $endgroup$



        Hint: We can substitute $x=t^6$ to obtain
        $$
        lim_{tto 1}frac{3}{1-t^3}-frac{2}{1-t^2}=lim_{tto 1}frac{1}{1-t}left(frac{3}{t^2+t+1}-frac{2}{1+t}right).
        $$







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Jan 24 at 10:50









        SongSong

        16.6k11043




        16.6k11043






























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