SEQUENCE AND SERIES

Definition:


Let f:N->R be a function and let f(n)=an.  Then, a1,a2,a3,...,an,.... is called the sequences in R deter mind by the function f and it is denoted by (an).  an is called n-th term of the sequences.

RANGE:

The range of the function f, which is a subset of R is called the range of the sequence.

Examples:

i)       The f:N->R given by f(n)=n-power 2.  Determind the sequence 1,4,9,....n-power 2,....

ii)       f(n)=n determind the sequence 1,2,3,.....,n,......

iii)      f:N->R given by f(n)=(-1)power n -1,1,-1,1,.....(-1)power n,.........
          The range of the sequence is {1,-1}.
          The range of the sequence may be finite or infinite.

iv)      (-1)power n+1 determind sequence, 1,(-1),1,(-1),....(-1)power n+1,......

v)       The constant function f:N->R given by f(n)=1 determind sequence.
           1,1,1,1,.........
           Such a sequence is called constant sequence.
vi)      f(n)={n/2 if n is even
               {1/2 (1-n) if n is odd
           sequence, 0,1,-1,2,....n,-n,....
vii)     Let x belongs to R the f:N->R given by, f(n)=x power n-1 determind Sequence.
          1,x,x power 2,...........x power n-1,....
          is called Geometric Sequence.
viii)   Let a1=1, a2=2 and an=an-1+an-2 determind the sequence.
         1,1,2,3,5,8,13,21,34,............ is called fibonacci series.
         Let a1= root 2 and an+1= root of (2+an) determind the sequence. 
          

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