Determine all nonnegative integers $r$ such that it is possible for an infinite geometric sequence to contain exactly $r$ terms that are integers. Prove your answer.

Respuesta :

Let, the geometric sequence is such that, value of common ratio is less than 1.

The Sequence is

 [tex]6^{n-1},6^{n-2},6^{n-3},.....,.......\infinity.[/tex]

The Geometric Squence is infinite geometric sequence, as there are uncountable terms in the sequence.

⇒So, From  [tex]6^{n-1}[/tex], to infinity, there will be n terms which will be integers when , n≥1.

⇒Put, n=1,

Number of terms which are Positive Integers =1 which is [tex]6^{n-1}[/tex].

⇒When, n=2

Number of terms which are Positive  Integers =2 which is [tex]6^{n-1},6^{n-2}[/tex].

⇒When, n=3

Number of terms which are Positive Integers =3, which is [tex]6^{n-1},6^{n-2},6^{n-3}[/tex].

..........

So,⇒ when , n=r

Number of terms which are Positive Integers =r, which is [tex]6^{n-1},6^{n-2},6^{n-3},6^{n-4},........6^{n-r}[/tex].