Direct Comparison Test inequality help

dami
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Homework Statement



Explain why the Direct Comparison Test allows us to use the inequality Ln n < n^(1/10) even though it is not true for a great many n values.

Homework Equations





The Attempt at a Solution


I looked at the graphs of Ln (n) vs. n^(k)
 
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dami said:

Homework Statement



Explain why the Direct Comparison Test allows us to use the inequality Ln n < n^(1/10) even though it is not true for a great many n values.

Homework Equations





The Attempt at a Solution


I looked at the graphs of Ln (n) vs. n^(k)
And what did you find out?

Also, how did you graph nk?
 


Actually, ln n < n^{1/10} is only true for n < 3 (for integer values of n).
 


dami said:
Actually, ln n < n^{1/10} is only true for n < 3 (for integer values of n).
That is incorrect. The statement ln n < n.1 is true for n = 3, and it is also true for a lot of much larger values.

In this problem you're supposed to provide justification for the assertion that ln n < n.1 for some infinitely long interval.
 


Thanks. Just realized I have been looking at the question the wrong way
 


Just plotted the graph
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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