Question

Which term of the AP:121,117,113,....,Is its first negative term? (Hint.find n for an <0

Answer 1

Hi

Here is ur answer

a = 121

d = -4   (∵ 117 - 121)

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.

an = a + (n-1)d

a32 = 121 + (31)-4

       = 121 - 124

∴ a32 = -3

Hope it helps U