Given A.P is 121, 117, 113, ………..
Fiat term (a) = 121
Common difference (d) = 117 – 121
= – 4
We know that, nth term an = a + (n – 1)d
And, for some nth term is negative i.e., an < 0
121 + (n – 1) – 4 < 0
121 + 4 – 4n < 0
125 – 4n < 0
4n > 125
n > 125/4
n > 31.25
The integer which comes after 31.25 is 32.
∴ 32nd term in the A.P will be the first negative term.