Question

Need help with explicit rule. Please help.

Answer 1

An = 74(1.07)^n-1

Explanation:

Here, we want to get the explicit rule

We are told that the sequence is geometric

At hour 4, we have that this is the 4th term

With conformance to the rule of geometric progression;

T4 = ar^3

90 = ar^3

for the 6th hour, this is the sixth term

103 = ar^5

dividing the 6th term by the 4th term, we have that

103/90 = ar^5/ar^3

103/90 = r^2

r = 1.07

To get a, we simply use any of the terms to substitute

using;

ar^3 = 90

a = 90/r^3

a = 90/1.07^3

a = 73.5 which is approximately 74

So the explicit rule is as follows;

An = 74(1.07)^n-1