Discuss the Behaviour of the Geometric Sequence (r power n)

Proof:

Case (i):  

Let, r =0.  Then, (r power n) Reduces to the constant sequence.  0,0,0,.... and hence convergences to 0.

Case (ii):

Let, r =1.  In this case (r power n) reduces to the constant sequence.  1,1,1,...... and hence convergences to 1.

Case(iii): 

Let, r =-1.  In this case (r power n) reduces to the -1,1,-1,1,.... which oscillate finiting the Oscillate Sequence.

Case(iv):

Let, r >1, then 0<1/r<1.  And hence (1/r power n)->0.  Therefore, (r power n) -> infinity.

Case(v):

Let, r <-1, then the terms of the sequence.  r power n are alternatively posititve and negative.  Also, mod r >1.  And hence by, Case(iv) (mod r power n) is unbounded.  Therefore, (r power n) Osciallates infinitely.

Case(vi):

Let, 0< r <1.  In this case, (r power n) is a monotonnic decreasing sequence and (r power n) >0 for all n belongs to N.  Therefore, (r power n) is a monotonnic decreasing and bounded below and hence (r power n) convergence.  Let ( r power n) -> l.  Since r power n>0 for all n,l >0------(1).

Claim:

l =0.  Let excellon >0 be given.  Since (r power n)->l,  there exist m belongs to N there exist l < r power n< l+ excellon for all n>=m.  Fix n>m, then l <r power n+1-----(2).
Also, r power n+1 =r.r power n < r( l +excellon)----(3).
Therefore, l < r ( l + excellon) by (2) and (3).
                l < (r/1-r) excellon.
          Therefore, this is true.
for every excellon >0, 
we get, l <=0----(4).
Therefore, l = 0 (by (1)and (4))

Case(vii):

Let, -1 < r < 0.
Then, r power n=(-1) power n .mod r power n   [when 0 <mod r < 1]
By case (vi)  (mod r power n) ->0.
Therefore, Alse ((-1)power n) is bounded sequence.
Therefore, ((-1)power n.mod r power n) ->0.
Therefore, ( r power n) ->0.

Hence the statement.


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