Question

b1-b2=8,b2+b3=12,b1 si q ? Progresi geometrica (am nevoie urgenttt , va rog ajutatima)

Answer 1

Răspuns:

Explicație pas cu pas:

b₁-b₂ = 8

b₂+b₃ = 12

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b₁-b₁q = 8

b₁q+b₁q² = 12

b₁(1-q) = 8 => b₁ = 8/(1-q)

b₁q(1+q) = 12 =>

8q(1+q) = 12(1-q) =>

2q+2q² = 3-3q =>

2q²+5q-3 = 0  =>

q₁,₂ = [-5±√(25+24)]/4

q₁,₂ = (-5±7)/4

q₁ = -3 ; q₂ = 1/2

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q₁ = -3 => b₁ = 2

q₂ = 1/2 => b₁ = 16