Respuesta :

It's a geometric sequence

  • common ratio=r=84/21=4
  • First term 1.3125

Formula:&

[tex]\\ \sf\longrightarrow a(n)[/tex]

[tex]\\ \sf\longrightarrow ar^{n-1}[/tex]

[tex]\\ \sf\longrightarrow 1.3125(4)^{n-1}[/tex]