Respuesta :

a given term in a PG =a₁rⁿ⁻¹

Let' calculate the 1st term a₁, knowing a term & the common factor/ratio

a₄ = 1/2 so 1/2 = a₁(1/2)³

1/2 = a₁/8 and a₁ = 4

Now calculate a₉ =a₁.r⁸

a₉ = 4.(1/2)⁸ and a₉ = 1/64