Q2 of 85 Page 101

Determine if the following sequences represent an A.P., assuming that the pattern continues. If it is an A.P., find the nth term:

5, –5, 5, –5, ...

Formula Used.


dn = an + 1 – an


In the above sequence,


a = 5;


d1 = a2–a1 = (–5)–5 = –10


d2 = a3–a2 = 5–(–5) = 10


d3 = a4–a3 = (–5)–5 = –10


⇒ As in A.P the difference between the 2 terms is always constant


But the difference in sequence is not the same.


∴ The above sequence is not A.P


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