Solution:

Let a – d , a, a + d are the first three terms.

Sum of three terms = 6

a – d + a + a + d = 6

3a = 6

a = 6/3

a = 2

Product of three terms = -120

(a – d) a (a + d) = -120

a (a²-d²) = - 120

2 (2² –d²) = -120

2(4 - d²) = -120

(4 - d²) = -120/2

(4 - d²) = -60

- d² = -60 – 4

- d² = -64

d = √64

d = ± 8

a = 2 d = 8 a = 2 d = -8

-6 , 2 , 10 10,2,-6

Therefore the three terms are -6 , 2 , 10 or 10,2,-6