Maths problem: how to do, thanks?
回答 (1)
2020-08-01 8:19 pm
✔ 最佳答案
Let its 1st term = a, common ratio = r T(1) + T(2) = 1
a + ar = 1
a(1+r) = 1 . . . . . . . . . . . . . ①
T(6) + T(7) = -32
ar⁵ + ar⁶ = -32
ar⁵(1+r) = -32 . . . . . . . . . . ②
②/①: r⁵ = -32 => r = -2
Put r = -2 into ① : a(1+-2) = 1
∴ 1st term, a = -1
收錄日期: 2021-04-24 08:04:22
原文連結 [永久失效]:
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