Mathematics
Find the nth term of the A.P. 13, 7, 1, -5, -11, ……. Using it, find its
(i) 9th term
(ii) 16th term.
AP
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Answer
Given,
a = 13
d = 7 - 13 = -6
nth term of an A.P. is given by,
an = a + (n - 1)d
an = 13 + (n - 1)(-6)
= 13 - 6n + 6
= 19 - 6n.
(i) 9th term
⇒ a9 = 13 + (9 - 1).(-6)
= 13 + 8(-6)
= 13 - 48
= -35.
(ii) 16th term
⇒ a16 = 13 + (16 - 1).(-6)
= 13 + (15).(-6)
= 13 - 90
= -77.
Hence, nth term = 19 - 6n, 9th term = -35 and 16th term = -77.
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