What is the 7th term of the geometric sequence where a1 = -2 and a5 = -512?

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Answer 1 · 2015-12-06T14:45:42

$q = + 4 Rightarrow a_6 = - 2048$
$q = - 4 Rightarrow a_6 = + 2048$

$a_n = a_0 * q^n$

$a_1 = a_0 q = -2$

$a_5 = a_0 q^5 = -512$

$a_5/ a_1 = q^4 = frac{-512}{-2} = 256 = 2^8$

$q = ± 4$

$a_1 = a_0 (±4) = -2 Rightarrow a_0 = ± (- 1/2)$

$a_6 = a_5 * q = -512 * (±4) = ± (- 2048)$