math questions
2011-09-27 4:49 am
the sum of the first two terms of a geometric sequence is 5 and the sum to infinity of the sequence is 9 .Find the possible values of the common ratio?
回答 (2)
2011-09-27 4:55 am
✔ 最佳答案
a + ar = 5...(1)a/(1 - r) = 9...(2)
From (2) a = 9(1 - r)
From (1) a = 5/(1 + r)
So, 5/(1 + r) = 9(1 - r)
-9(r^2 - 1) = 5
9r^2 = 4
r = -2/3 or 2/3
2011-09-27 5:23 am
a + ar = 5...(1)
a/(1 - r) = 9...(2)
From (2) a = 9(1 - r)
From (1) a = 5/(1 + r)
So, 5/(1 + r) = 9(1 - r)
-9(r^2 - 1) = 5
9r^2 = 4
r = -2/3 or 2/3
hopeｉcan help you
a/(1 - r) = 9...(2)
From (2) a = 9(1 - r)
From (1) a = 5/(1 + r)
So, 5/(1 + r) = 9(1 - r)
-9(r^2 - 1) = 5
9r^2 = 4
r = -2/3 or 2/3
hopeｉcan help you
收錄日期: 2021-04-26 14:55:56
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