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Question
For an A.P., t4 = 12 and its common difference d = – 10, then find tn
Solution
t4 = 12, d = – 10 .....[Given]
Since tn = a + (n – 1)d,
t4 = a + (4 – 1)(– 10)
∴ 12 = a + 3(– 10)
∴ 12 = a – 30
∴ a = 42
tn = a + (n – 1)d
= 42 + (n – 1)(– 10)
= 42 – 10n + 10
= 52 – 10n
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