Answer:
[tex]\boxed{f(n) = 4n + 16 }[/tex]
.
Step-by-step explanation:
We know that it is arithmatic squence
with a = 20 and b = 4
.
So
[tex]Un = a + (n - 1)b[/tex]
[tex]Un = 20 + (n - 1)4[/tex]
[tex]Un = 20 + 4n - 4[/tex]
[tex]Un = 4n + 16[/tex]
.
Happy to help :)
