Question

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

Answer 1

here An =0
a+(n-1)d=0
121+(n-1)4=0
(n-1)=-121
n=-121+1
n=-120

Answer 2

Hii friend!!

a= 121
d= -4
find which term is 0
T = a + ( n-1 ) d
0 = 121 + ( n- 1) (-4)
-121 = (n-1) (-4)
-121 = -4n +4
-121 -4 = -4n
-125 = -4n
n = -125/-4
n= 31.25
n = 31
31st term is 0 then next term is negative
so 32nd is the first negative term

hope it will help you