Answer:

A₁, A₂, A₃, A₄, A₅, A₆ – 7 AM between 15 and – 13

15, A₁, A₂, A₃, A₄, A₅, A₆, – 13 are in AP

a_n = a + (n – 1)d

a_n = -13, a = 15, n = 8

-13 = 15 + (8 – 1)d

-13 = 15 + 7d

7d = -13 – 15

7d = -28

d = -4

A₁ = a + d = 15 – 4 = 11

A₂ = A1 + d = 11 – 4 = 7

A₃ = A2 + d = 7 – 4 = 3

A₄ = A3 + d = 3 – 4 = -1

A₅ = A4 + d = -1 – 4 = -5

A₆ = A5 + d = -5 – 4 = -9