Thursday, September 6, 2018

real analysis - Proving that if limnrightarrowinftyan=a then limnrightarrowinftya2n=a2




If we have a real sequence |an| such that limnan=a, how do we prove (by an ϵN argument) that |an| such that limna2n=a2?



I know you can use algebra to do to the following:



|a2na2|=|(ana)(an+a)|



Where I feel like you can use the implication that limnan=a to show that (ana)<a or something.



What's the proper way to go about this?


Answer




Hint



A convergent sequence is bounded. So you can also bound |a+an|.


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