4, 3, 2, 1, ....

(vii) 4, 3, 2, 1, .... (1 mark)

Sol. t1 = 4, t2 = 3, t3 = 2, t4 = 1,

t2 – t1 = 3 – 4 = – 1

t3 – t2 = 2 – 3 = – 1

t4 – t3 = 1 – 2 = – 1

Here, The difference between ANY two consecutive terms is –1 which is constant.

∴ The sequence is an A.P.