Answers

2016-02-24T16:04:46+05:30

Here a = 150, d = 116 – 120 = – 4
nth term of an AP is tn = a + (n – 1)d
= 120 + (n – 1)(– 4)
= 120 – 4n + 4
= 124 – 4n
Since we need negative term, tn < 0
124 – 4n < 0
⇒ 124 < 4n
⇒ 31 < n
That is n > 31
Hence n = 42
Therefore the 42nd term is first negative term.
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