Maximum Likelihood Estimator for a function

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Homework Statement



Consider the following density function:
f(x) = ABB/xB+1; A<= x, zero elsewhere, where A > 0 and B> 0

Homework Equations




The Attempt at a Solution



f(x1,...,xn)= ABnBn(x1...xn)B+1

ln f(x1,...,xn)= Bn ln A + n ln B + (B+1)ln((x1...xn)

After differentiating with respect to A and setting to 0, Bn/A= 0. Therefore there is no maximum likelihood estimator for A?
 
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Where did all of the different "x"s come from? You seem to have your original density function to a power. Why?

Also please state the entire problem. Are you asking for the "maximum likelihood estimator of A?
 
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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