DJHJA wrote:In the infinite sequence, a1, a2, a3........a(n) each term after the first is equal to twice the previous term,
if a5 - a2=12, what is the value of a1?
a. 4
b. 24/7
c. 2
d. 12/7
e. 6/7
ans is 6/7.. this is a pretty easy question, not sure y i cant get it
can anyone help?
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To get from a2 to a5, we need to multiply by 2 three times.
Thus, a5 = 2*2*2*a2 = 8a2.
Substituting a5 = 8a2 into a5 - a2 = 12, we get:
8a2 - a2 = 12.
7a2 = 12.
a2 = 12/7.
Since a2 = 2a1, we get:
12/7 = 2a1
a1 = 6/7.
The correct answer is
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