Friday, 26 August 2016

limits - Evaluate limxtoinftyln(x3+x)




Evaluate limxln(x3+x).




I was wondering if I can solve this limit in this way:
limxln(x3+x)=limxln[x3(1+1x2)].




At this point, I just considered ln(x3) because 1 doesn't make any difference and 1/x2 tends towards 0.
So, the result will be 0. And I found it because I know the graph of the logarithm of x to the power of an odd number. So, my second question is, is it possible to understand what the result of limxln(x3) algebraically without thinking of the graph?



Any suggestion and help will be appreciated.
Thank you in advance and have a good day :)


Answer



The correct way is



limxln(x3+x)=limxln[x3(11x2)]=limx[lnx3+ln(11x2)]==limxlnx3+limxln(11x2)=++0=+




indeed



limxlnx3=limx3lnx=limy+3lny=+


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