Which term of AP:121,117,113,......., is its first negative term?

a=121, d=-4, let a_{n}=0

a_{n}=a+(n-1)d

0=121+(n-1)(-4)

-121=-4n+4

-125=-4n

n=31.25

since n has to be a whole no., therefore, the ans is 32 ( the no. next to 31.25)

hence the 32nd term is the first negative term