Answer:
a(n)=80*(9/10)^(n-1)
Step-by-step explanation:
I think u r confused
this sequence is geometric not arithmetic
HOw we know that ??
when we get a common difference that must Be equal
d=72-80=-8 not equal to d=64.8-72=-7.2
So it is not arithmetic
but when we get the common ratio that also must be equal
r=72/80=9/10 equal to r=64.8/72=9/10
So it is geometric
By using this equation:
a(n)=a*r^(n-1)
and we have a=80 , r=9/10
Then a(n)=80*(9/10)^(n-1)
I really hope this helps <3
