Which of the following are APs? If they form an AP, find the common difference d and write three more terms.
a, 2a, 3a, 4a, . .
a, 2a, 3a, 4a, ........
a2 – a1 = 2a – a = a
a3 – a2 = 3a – 2a = a
a4 – a3 = 4a – 3a = a
i.e., ak + 1 – ak is the same every time. So, the given list of numbers form an A .P. with the common difference d = 0.
The next three terms are :
4a + a = 5a, 5a + a = 6a
and 6a + a = 7a.