Răspuns:
19/32
Explicație pas cu pas:
b₁ = 1 ; q = -1/2 ; n = 6
bₙ = ? => b₆ = ?
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b₁ = 1 ; b₂ = b₁q = -1/2 ; b₃ = b₂q = (-1/2)·(-1/2) = 1/4
b₄ = b₃q = 1/4 ·(-1/2) = -1/8
b₅ = b₄q = (-1/8)·(-1/2) = 1/16
b₆ = b₅q = 1/16 ·(-1/2) = -1/32
S₆ = b₁+b₂+b₃+b₄+b₅+b₆
S₆ = ²⁾1-1/2+²⁾1/4-1/8+²⁾1/16-1/32
S₆ = ¹⁶⁾1/2 +²⁾1/8 + 1/32 = 19/32
