What are the conditions for a sequence to be an AP?
Difference between two consecutive numbers should be same.
Let a1 , a2 , a3 , a4 , a5, a6, a7, a8… be a sequence.
For this sequence to be an AP, the difference between any two consecutive terms should be constant.
a2–a1=a3–a2=a4–a3=d
This difference is called the common difference of the AP and is denoted by d.
So an AP with the first term a can also be represented in this form as well a, a+d, a+2d,...