To check -150 is present in the sequence
-150=a+(n-1)d
According to the given series
a=11,d=-3
So we need to find n
If n is a fraction then it does not belongs to that series
From formula=-150=11+(n-1)-3
-150=11-3n+3
-150=14-3n
-150-14=-3n
-164=-3n
n=164/3
We got n as a fraction so -150 does not belong to series
