Question

Which of the following is the formula for the geometric sequence?
3, 15, 75, 375 ...
A. an=3(5)n-1
B. an=5(3)n-1
C. an=12(3)n-1
D. an=5(12)n-1

Answer 1

the general formula for a geometric sequence is ..
\[A_{n} = ar^{n-1}\]
where
a = the first term
r = the common ration

the first term of the sequence is 3..

to find the common ration u have to divide 2 successive terms
r = 15/3 = 5

so... the equation is
\[A_{n} = 3. 5^{n-1}\]
not it :) ?

Answer 2

*srry... i mean got .. not "not " XD

Answer 3

yea, i got it. thanks .