Answer:
a(1) = 72
a(n) = a (n-1) - 18
Step-by-step explanation:
This is a simple series of multiplication of 18 . If we divide all the numbers by 18 we get
72/18, 54/18, 36/18. 18/18, 0/18
4 , 3 , 2 , 1 , 0
So we can see that the numbers are in decreasing order as the multiples of 18.
in other words the first term is a= 72
from which we subtract 18 and get 54 and so on.
So the general rule would be
a(1) = 72
a(n) = a (n-1) - 18
Where n and (n-1 ) are subscripts. We are just subtracting 18 from the number to get the answer.
72-18= 54
54-18= 36
36-18= 18
18-18=0
