Question

Dada a progressão geométrica (1,3,9,27,...), calcular:
a)a12;
b)o valor de N para an=. 19683

Answer 1

PG = (1,3,9,27,...)

a₂ = a₁ · q

3 = 1 · q

q = 3

a) aₙ = a₁ ⋅ qⁿ⁻¹

  a₁₂ = a₁ · q¹¹

   a₁₂ = 1 · 3¹¹

  a₁₂ = 177147

b) aₙ = a₁ ⋅ qⁿ⁻¹

   19683 = 1 ⋅ 3ⁿ⁻¹

   3⁹ = 3ⁿ⁻¹

   9 = n - 1

  n = 10