Some numbers arranged in a definite order according to the definite rule, are said to form a sequence.
The number occurring at the nth place of a sequence is called its inert term denoted by Tn or An.
Example- consider the rule
Tn = ( 2n + 1 )
Putting n = 1,2,3,4,5…., we get
T1=3, T2=5, T3=7, T4=9 and so on…
Thurs the number 3,5,7,9… Form a sequence.
In the sequence the first term is 3 the second term is 5 the third term is 7 and so on.
This was an example of AP.
A sequence in which each term differs from its preceding term by a constant is called an arithmetic progression, written as AP. This constant is called the common difference of the AP.