Help me to understand the solution..or give a new shorter solution

Find \lim_{n\rightarrow \infty}{\frac{a^n}{n!}}

I have this soln available with me..

plz provide a new shorter soln..or help me to understand this soln..

8 Answers

1
Arshad ~Died~ ·

if we consider
a^n/n!
then with each increasing value of n
a^n/n!
decreases by factor of a/n+1 of the previus term
now for any value of a if n>4 the value of a^n/n! becomes less than 1
(u change check that by taking any arbitrary value of a)
so if n→infinity
a^n/n! is less than 0
and hence tends to 0 in the neighbourhood

24
eureka123 ·

I think thats what has been done in my solution...hasnt it ??

1
Arshad ~Died~ ·

yes thats what has been done but in a other way......just to make it look difficult to students.........

62
Lokesh Verma ·

Let tn=an/n!

tn+1/tn = a/(n+1)

when n goes to infinity, this ratio goes to zero...

Hence, the limit is zero :)

24
eureka123 ·

if tn→0
then tn+1 must also →0
so can we have this tn+1/ tn ????
isnt it of 0/0 form ??

Or am I acting like a fooool :P

62
Lokesh Verma ·

lol.. no no

see we dont have to find tn+1/ tn

What i have tried to do is to find this limit..

Thus, no matter what the value of tn be,

tn+1=tn × tn+1/tn

In a very stupid way to explain:

if the limit exists, tn will be finite.. and tn+1 will be zero times tn

24
eureka123 ·

kkkk..

got it...

66
kaymant ·

In general note that for large positive integer n,
log n < xn < an < n!

That is the factorial increases faster than the exponential which in turn increases than the power function while the logarithm is the slowest among all.

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