Find a formula for this sequence

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Homework Statement


A sequence (xj) where j can go from 0 to infinity satisfies the following:
(1) x1= 1 and
(2) for all m≥n≥0, xm+n+ xm-n= (1/2)(x2m+x2n)
Find a formula for xj and prove that the formula is correct


Homework Equations





The Attempt at a Solution


All I have done so far is is play around with m and n values so far and I think a proper formula:
xj= j2. Now I would have to prove this (for which I plan to use induction most likely) but I wanted to see if I was on the write track in my thinking.
 
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nate9228 said:

Homework Statement


A sequence (xj) where j can go from 0 to infinity satisfies the following:
(1) x1= 1 and
(2) for all m≥n≥0, xm+n+ xm-n= (1/2)(x2m+x2n)
Find a formula for xj and prove that the formula is correct


Homework Equations





The Attempt at a Solution


All I have done so far is is play around with m and n values so far and I think a proper formula:
xj= j2. Now I would have to prove this (for which I plan to use induction most likely) but I wanted to see if I was on the write track in my thinking.

Looks fine to me. Now try and check it. Induction isn't really necessary. Just check that your guess works.
 
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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