Which of the following form of an AP? Justify your answer.
–1, –1, –1, –1, ….
We have a1 = - 1 , a2 = - 1, a3 = - 1 and a4 = - 1
a2 - a1 = 0
a3 - a2 = 0
a4 - a3 = 0
Clearly, the difference of successive terms is same, therefore given list of numbers from an AP.