(Q16).Which of the following forms an AP? If they form an AP, then write the next two terms?

(i) 1, – 1, – 3, – 5, . . .

a2 – a1 = – – = –

a3 – a2 = – – ( – ) = – + = –

a4 – a3 = – – ( – ) = – + = –

i.e., ak + 1 – ak is same every time

So, the given list of numbers forms an AP with the common difference d = -.

The next two terms are: – 5 + (– ) = – and – + (– ) = – .