Real Analysis: Hardy Littlewood

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Homework Statement


Establish the Inequality ##f^*(x)\ge \frac{c}{|x|ln\frac{1}{x}}## for
##f(x)=\frac{1}{|x|(ln\frac{1}{x})^2}## if ##|x|\le 1/2## and 0 otherwise

Homework Equations


##f^*(x)=\sup_{x\in B} \frac{1}{m(B)} \int_B|f(y)|dy \quad x\in \mathbb{R}^d##

The Attempt at a Solution


Disregard, I figured it out.
 
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What was the sticking point that you overcame?
 
I was stuck on the first step. I was able to work in reverse from the solution but felt like I was missing a key idea doing it that way. Namely,

##\sup_{x\in B} \frac{1}{m(B)} \int_B \frac{1}{|x|(ln\frac{1}{x})^2}\ge \frac{1}{2|x|}\int_{-|x|}^{|x|} \frac{1}{|x|(ln\frac{1}{x})^2}##

from there you just work out the integral.
 
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Likes jedishrfu
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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