Question

Which sequence is a geometric progression

a 2 4 6 8
b 1 1 2 3
c1 2 4 8
d1 3 5 7​

Answer 1

9514 1404 393

Answer:

c 1, 2, 4, 8

Explanation:

It can work well to look at the first differences.

a: 4 -2 = 2; 6 -4 = 2 ⇒ differences are 2, 2, 2

b: differences are 0, 1, 1

c: differences are 1, 2, 4

d: differences are 2, 2, 2

__

Sequences 'a' and 'd' have common differences that are constant. These are arithmetic sequences. Sequence 'b' is of no named type.

Sequence 'c' has first differences that have a common ratio, the same as the sequence itself. This is an indication the sequence is geometric. The ratios of values are 2/1 = 2; 4/2 = 2; 8/4 = 2, so the terms have a common ratio.

Sequence c is a geometric progression.