– 10, – 13, – 16, – 19, .....

(viii) – 10, – 13, – 16, – 19, ..... (1 mark)

Sol. t1 = – 10, t2 = – 13, t3 = – 16, t4 = – 19

t2 – t1 = – 13 – (– 10) = – 13 + 10 = – 3

t3 – t2 = – 16 – (– 13) = – 16 + 13 = – 3

t4 – t3 = – 19 – (– 16) = – 19 + 16 = – 3

 Here, The difference between ANY two consecutive terms is – 3 which is constant.

∴  The sequence is an A.P.