中等MATH-EXPL-011
Which sequence is geometric?
A. 2, 4, 6, 8
B. 2, 6, 18, 54✓ 答案
C. 1, 3, 5, 7
D. 5, 5, 5, 10
解說
Each term of 2, 6, 18, 54 is 3 times the previous term, so the common ratio is 3. The sequences with a fixed difference are arithmetic. The last list is constant and then jumps, so it has no single common ratio.