Answers

  • Brainly User
2016-07-11T14:24:35+08:00
Common ratio (r) :
-32/64 = -1/2
16/-32 = -1/2
-8/16 = -1/2

an = a₁(r)ⁿ⁻¹

a₉ = 64 (-1/2)⁹⁻¹

a₉ = 64 (-1/2)⁸

a₉ = 64 (1/256)

a₉ = 64/256

a₉ = 1/4  ⇒    ANSWER

To check:
a₅ = (-8)(-1/2) = 4
a₆ = (4)(-1/2) = --2
a₇ = (-2) (-1/2) = 1
a₈ = (1) (-1/2) = (-1/2)
a₉ = (-1/2) (-1/2) = 1/4        a₉ = 1/4
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