Question

Write the formula for the geometric sequence.
5, 10, 20, 40, …
A. an=40∙2n-1
B. an=40∙2n
C. an=5∙2n-1
D. an=5∙2n

Answer 1

@LukeBlueFive

Answer 2

did u find the common ratio ?

Answer 3

a_1 = 5
a_2 = 10

r = common ratio

\[r= \frac{ a_{2} }{ a_{1} }\]

Answer 4

the formula for a geometric progression
\[A_{n} = a \ r^{n-1}\]
simple "a" = the first term = 5
so...
\[A_{n} = 5 \ r^{n-1}\]
after u find r plug it in to the equation and that is ur answer :)

Answer 5

Yeah i think so is it 0.5?

Answer 6

oh ok is it 0.5?

Answer 7

@***[ISURU]*** ?

Answer 8

In order to get r (the ratio), divide any of the terms by the previous term (40/20, 20/10, 10/5). That will give you r. Then, plug that value for r into Isuru's formula to get the answer.