A1) →Г.4 ; q = -2
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A2) →Б. -3 . ; q = b₂ /b₁ =12 /(-4) = -3
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A3) →A. -1536. ; b₅
=b₁*q⁴ = (-6)*4⁴ = (-6)* 256 = - 1536.
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A4) →Б. - 4374 ; b₇ =b₁*q⁶ = (-6)*(-3)⁶ = - 4374.
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A5) → Б. - 340 ; S₈ = b₁(q⁸-1) /(q -1) =4 ((-2)⁸ -1) / (-2-1) = -340.
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A6) →Б. -30 ; S = b₁/(1 -q) = -6/(1-4/5) = -30.