What is the 6th term of the geometric sequence where a1 = -4,096 and a4 = 64? A. -1 B. 4 C. 1 D. -4?
回答 (2)
2016-08-02 7:21 pm
Let r be the common ratio of the geometric sequence.
a₁ = -4096
a₄ = 64
-4096 × r³ = 64
r³ = -64/4096
r³ = -1/64
r = -1/4
a₆ = a₁ r⁵
a₆ = -4096 × (-1/4)⁵
a₆ = 4
...... The answer: B. 4
a₁ = -4096
a₄ = 64
-4096 × r³ = 64
r³ = -64/4096
r³ = -1/64
r = -1/4
a₆ = a₁ r⁵
a₆ = -4096 × (-1/4)⁵
a₆ = 4
...... The answer: B. 4
2016-08-02 7:21 pm
a_4 = a_1 * r^(4 - 1)
64 = -4096r^3
-1/64 = r^3
r = -1/4
a_6 = a_4 * (-1/4)^(6 - 4)
a_6 = 64 * 1/16 = 4
64 = -4096r^3
-1/64 = r^3
r = -1/4
a_6 = a_4 * (-1/4)^(6 - 4)
a_6 = 64 * 1/16 = 4
收錄日期: 2021-04-18 15:24:03
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