Question

which term of the AP: 121,117,113......,Is its first negative term?

Answer 1

Answer:

a=121

d= -4

Let an=0

an=a+(n-1)d

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

-121=(n-1)*-4

n-1=121/4=30.25

n=31.25

Therefore the first negative term is the 32nd term

Answer 2

a = 121

d = -4

let an= 0

then

an = a + (n-1)d

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

=> 0 = 121 - 4n + 4

=> 4n = 125

=> n = 125/4

=> n = 31.25

as n must be natural number then n= 32

32nd term is First negative number.

a32 = 121 + (31)-4

= 121 - 124 = -3