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, 15, 25, 35, 45, ...

Formula Used.


dn = an + 1 – an


an = a + (n–1)d


In the above sequence,


a = 5;


d1 = a2–a1 = 15–5 = 10


d2 = a3–a2 = 25–15 = 10


d3 = a4–a3 = 35–25 = 10


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


The difference in sequence is same and comes to be 10.


The above sequence is A.P


The nth term of A.P is an = a + (n–1)d


an = a + (n–1)d = 5 + (n–1)10


= 5 + 10n–10


= –5 + 10n


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