g.b

Asked by PRAMOD | 7th Dec, 2013, 05:50: PM

Expert Answer:

The given A.P is 121, 117, 113…
Here, first term a = 121 and common difference, d = –4.
Let nth term be the first negative term of the given A.P
∴ an < 0
121 + (n – 1) (–4) < 0 (an = a + (n – 1) d)
–4n + 125 < 0
– 4n < – 125
n > 31.25
 
∴ n = 32 [Since n is a natural number]
 
Thus, 32nd term is the first negative term of the given A.P.

Answered by  | 7th Dec, 2013, 07:07: PM

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