Consider the following arrangement of numbers 3,6,9,12,.....
These numbers are arranged according to a specific rule. If you observe the rule, you will find that every next number to the previous one is obtained by adding 3(except the first one).
What is a sequence?
A sequence is an arrangement of numbers in specific order like the above one.
Now, what is an arithmetic progression?
A special type of sequence in which every term except the first is obtained by adding a fixed number which may be positive/negative to the preceding term.
A general A.P. (Arithmetic Progression) is given by a , a+d , a+2d , .....a+(n-1)d
where a is the first term , d is the common difference, n is the total number of terms.
General /nth term/last term of an A.P is given by an = a +(n-1) d
Example :Find the common difference and nth term of the given A.P.
-5 , -1, 3 ,7 ......
Here a = -5
d = -1-(-5) = -1+5 = 4
So, an = a+ (n-1)d
= -5+(n-1)4
= -5+4n-4
= 4n-9
Visual representation of sequences....
Let us consider the following sequences
(1) 4,6,8,10,......... Geometrically its representation could be like a ladder in which the height of each step from the first step is same.
(2) 3,6,8,10,.......... Geometrically, its representation is like steps as shown below, but the difference of heights between two consecutive steps ia not always same.
