Thursday, May 11, 2017

proof verification - How to calculate this limit limlimitsntoinftyleft[left(n+frac32right)frac13left(n+frac12right)frac13right]?



I tried rationalizing this [multiplying and dividing by (n+32)13+(n+12)13 but then the numerator contains terms of power 23. So I couldn't move forward.



What are methods to evaluate this?




PS : While typing this question I got this,



(n+32)13(n+12)13=(1+32n)13(1+12n)13n13.



Now I apply L'hospital rule and get,



limn[(n+32)13(n+12)13]=limn12n23[(1+32n)23(1+12n)23]=0.



Am I right?


Answer




HINT:
You should multiply and divide by (n+32)23+(n+32)13(n+12)13+(n+12)23 to rationalize this as
a3b3=(ab)(a2+ab+b2)
The rest should be simple...


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