Is it arithmetic?
Is 3 - 81 = 1/9 - 3 ? , Nope, so it is not arithmetic
Is it geometric?
is 3/81 = (1/9) / 3 ? , Yes, so it is geometric
to be arithmetic, there has to be a common "difference" between consecutive terms
to be geometric, there has to be a common "ratio" between consecutive terms,
which is true in your case, and that common ratio is 1/27
Which explains why the sequence 81,3,1/9,... is arithmetic or geometric?
I think it's geometric, but I not sure why It either because:
It decreases by 3 or It decreases by 1/27. I think it could be because it decreases 1/27.
2 answers
Thank you Reiny! you are extremely helpful! Bless you and have a good day!