Which term of the A.P. is its first negative term?

a = 121, d = -4

A_n = -ve

A_n= a + (n – 1) d

= 121 + (n – 1) -4

= 125 – 4n

Since, we want –ve term

Therefore, 4n should be a number greater than 125

Hence, 128 is the number greater than 125 and divisible by 4

4n = 128

n = 32

Therefore, 32^nd term of the given A.P. is –ve