- #1
Astronomer107
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I'm having trouble with these type of probles (where a negative log comes up):
(All of this is solving without sigma notation)
Find the number of terms in these geometric sequences and the sum of the numbers.
11, -22, 44,...,704
I know that a1 = 11, r = -2, and an = 704, so I did:
704 = 11(-2)^n-1 so,
64 = (-2)^n-1
log 64 = (log -2) n-1
n should = 7, but when I found the log of 64 divided by the log of -2, I got .2785219413 - 1.2...
Why is there a minus sign and what am I doing wrong? Please help. Thanks!
(All of this is solving without sigma notation)
Find the number of terms in these geometric sequences and the sum of the numbers.
11, -22, 44,...,704
I know that a1 = 11, r = -2, and an = 704, so I did:
704 = 11(-2)^n-1 so,
64 = (-2)^n-1
log 64 = (log -2) n-1
n should = 7, but when I found the log of 64 divided by the log of -2, I got .2785219413 - 1.2...
Why is there a minus sign and what am I doing wrong? Please help. Thanks!
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