Question

Find the general term of an ap whose 8th term is -2 and 15 term is 12​

Answer 1

Answer:

a(n) = 2n - 18

Step-by-step explanation:

a(n) = a(1) + (n-1)d

Given, a(8) = -2 and a(15) = 12

a(8) = a(1) + 7d = -2 ---(1)

a(15) = a(1) + 14d = 12 ---(2)

Subtracting eq 1 from 2,

7d = 12 - (-2) = 12 + 2 = 14

d = 2

Putting d = 2 in eq 1,

a(1) + (7×2) = -2

a(1) + 14 = -2

a(1) = -14 - 2 = -16

a(1) = -16

General form:

a(n) = -16 + (n-1)×2

= -16 + 2n - 2 = -18 + 2n