b₁ = - 25 b₂ = - 20 b₄ = ?
b₂ = b₁ * q
q = b₂ : b₁ = - 20 : (- 25) = 4/5
b₄ = b₁ * q³ = - 25 * (4/5)³ = - 5² * (4/5)³ = - 64/5 = - 12,8
b₁ = - 25 b₂ = - 20 b₄ = ?
b₂ = b₁ * q
q = b₂ : b₁ = - 20 : (- 25) = 4/5
b₄ = b₁ * q³ = - 25 * (4/5)³ = - 5² * (4/5)³ = - 64/5 = - 12,8