Question

In: Math

What are the first five terms of the geometric sequence a1 = 3, an = 4 ⋅ an − 1 ?

What are the first five terms of the geometric sequence a1 = 3, an = 4 ⋅ an − 1?

Solutions

Expert Solution

Consider a geometric sequence with recursive formula,

a1 = 3

an = 4 ∙an-1 ...... (1)

 

First term of given sequence is, a1 = 3

 

Substitute n = 2 and a1 = 3 in formula (1) an = 4 ∙an-1 and compute second term,

a2 = 4 ∙ a1

      = 4 × 3

     = 12

 

Substitute n = 3 and a2 = 12 in formula (1) an = 4∙an-1 and compute third term,

a3 = 4∙a2

     = 4 × 12

     = 48

 

Substitute n = 4 and a3 = 48 in formula (1) an = 4∙an-1 and compute fourth term,

a4 = 4∙a3

     = 4 × 48

     = 192

 

Substitute n = 5 and a4 = 192 in formula (1) an = 4∙an-1 and compute fifth term,

a5 = 4∙a4

     = 4 × 192

     = 768

 

Therefore, first five terms of given sequence is {3, 12, 48, 192, 768}.


Therefore, first five terms of given sequence is {3, 12, 48, 192, 768}.

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