Question

Find the 12th term of the geometric sequence 5, 20, 80, ...5,20,80

Answer 1

Answer:

a₁₂ = 20971520

Step-by-step explanation:

The nth term of a geometric sequence is

$a_{n}$ = a₁$(r)^{n-1}$

where a₁ is the first term and r the common ratio

Here a₁ = 5 and r = a₂ ÷ a₁ = 20 ÷ 5 = 4 , then

a₁₂ = 5 × $4^{11}$ = 5 × 4194304 = 20971520