Answer:
The given sequence is Algebraic (Arithmetic) with common difference is -9.
Explanation:
The given sequence is Arithmetic Sequence.
Arithmetic Sequence is a sequence in which every two neighbor digits have equal distances.
Geometric Sequence is the sequence in which every digit is the same multiplier of its previous digit.
The given sequence is: 81, 72, 63, 54,...
Here, First term(a) = 81, Second term(b) = 72
Common difference (d) = b - a = 72 - 81 = -9
Hence, Common difference is -9.