Monday, 24 February 2014

calculus - Proving that a function grows faster than another



I'm told to prove or disprove that 4n grows faster than 4n
As n tends to infinity.




From my Previous years Calculus I know that if I take the derivative of two functions, and one is bigger, than it must grow faster.



f(n)=4n



g(n)=4n



if
f(n) is > g(n) Then f(n) grows faster than g(n), as n



My Attempt:




f(n)=(ln(4)×4n))/2n



g(n)=(ln(4)×4n/2)/2



But Now I'm not sure if f(n) does grow faster, how would I know that it's first derivative is bigger here, just by plugging in numbers?


Answer



Hint: Look at the ratio 4n4n. This is equal to

(44n/2)n.


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