Solution:

In the above mentioned given series, A.P. 11, 8, 5, 2..

The first term, a = 11

The common difference, d = a₂−a₁ = 8−11 = −3

Let −150 be the n^th term of this A.P.

As we all know, for an A.P.,

a_n = a+(n−1)d

-150 = 11+(n -1)(-3)

-150 = 11-3n +3

-164 = -3n

n = 164/3

Clearly we see that, n is not an integer but a fraction.

Therefore, – 150 isn’t a term of this A.P.