Verified answer

b₁ = 1       b₂ = 5     bₙ = 125

b₂ = b₁ * q

q = b₂ : b₁ = 5

bₙ = b₁ * qⁿ⁻¹

125 = 1 * 5ⁿ⁻¹

5ⁿ⁻¹ = 5³

n - 1 = 3

n = 4

Ответ : b₄ = 125