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Question
The nth term of a sequence is (2n – 3), find its fifteenth term.
Solution
nth term of A.P = (2n – 3)
`=>` tn = 2n – 3
n ∈ N
n = 1, 2, 3, .....
a1 = 2(1) – 3
= –1
a2 = 2(2) – 3
= 1
a3 = 2 × 3 – 3
= 6 – 3
= 3
A.P. = –1, 1, 3
a = –1
a = 1 – (–1) = 2
an = a + (a – 1)d
a15 = a + (15 – 1)d
a15 = a + 14d
a15 = –1 + 14 × 2
a15 = –1 + 28
a15 = 27
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