Which term of AP:121,117,113,......., is its first negative term?
a=121, d=-4, let an=0
an=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