BOUNDED SEQUENCES
Analysis
 

6. DEFINITION OF A BOUNDED SEQUENCE

A sequence is said to be bounded if it has an upper bound and a lower bound.

13.- Note that in this sequence: 7 is an upper bound and -2 is a lower bound and therefore, when represented on the Cartesian plane, the points in the sequence are found between the lines y=7 and y=-2.

14.- Check that the same thing happens for any other upper or lower bound K and k, i.e. the points in the sequence are between the lines y=K and y=k. In other words, for any term n:

k

£

a

n

£

K

   

7. INFIMUM AND SUPREMUM

The greatest lower bound is known as the infimum and the least upper bound as the supremum.

15.- Find the supremum and infimum of the sequence in this window.

If the infimum is a term in the sequence it is called the minimum.

If the supremum is a term in the sequence it is called the maximum.

16.- Check that the sequence in the window has a maximum, as the supremum forms part of the sequence, but it does not have a minimum as the infimum does not form part of the sequence.

   

       
           
  Juan Madrigal Muga
 
Spanish Ministry of Education. Year 2002
 
 

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