Răspuns:
Explicație pas cu pas:
b₁ + b₂ = 28
b₃ + b₄ = 175 <=>
b₁+b₁q = 28 ; b₁q²+b₁q³ = 175 =>
b₁(1+q) = 28
b₁q²(1+q) = 175 =>
q² = 175/28 = 25/4 =>
q₁,₂ = ± 5/2
q₁ = -5/2 => b₁ = 28/(1-5/2) = 28/(-3/2) = -56/3
b₂ = 28-(-56/3) = ³⁾28+56/3 = 140/3
b₃ = 140/3 ·(-5/2) = -350/3
b₄ = -350/3 ·(-5/2) = 875/3
q = 5/2 => b₁ = 28/(1+5/2) = 28/(7/2) = 8
b₂ = 8·5/2 = 20
b₃ = 20·5/2 = 50
b₄ = 50·5/2 = 125
