Question

Which of the following sequences are in arithmetic progression?

15, 12, 9, 6, .....

Answer 1

15, 12, 9, 6, .....

d₁ = 12 – 15 = – 3

d₂ = 9 – 12 = – 3

d₃ = 6 – 9 = – 3

Since d₁ = d₂ = d₃, the given sequence is in arithmetic progression.