((i raised the points and this is multiple choice))
which sequences are geometric ?
choose all that apply

a) 100, 90, 80, 70, 60, . .
b) 320, 80, 20, 5, 1.25, . . .
c) 4, 9, 19, 24, 34, . .
d) 1/3, 2/3, 4/3, 8/3, 16/3, . .

B and D

Step-by-step explanation:

Geometric sequences and series. A geometric sequence is a sequence of numbers that follows a pattern were the next term is found by multiplying by a constant called the common ratio, r.

an = ar^(n-1)

d) 1/3, 2/3, 4/3, 8/3, 16/3, . . . .

1/3 * 2 = 2/3

2/3 * 2 = 4/3

4/3 * 2 = 8/3

where r = 2, constant multiplier is 2.  //Answer

b)  320, 80, 20, 5, 1.25, . . . . .

320 * 1/4 = 80

80 * 1/4 = 20

20 * 1/4 = 5

r = 1/4 //Answer

B and D

//Hope this helps.

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