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Topic: Common Core e-Text Done
Replies: 6   Last Post: Mar 21, 2014 8:45 AM

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Jamie D

Posts: 31
Registered: 9/17/13
Re: Common Core e-Text Done
Posted: Mar 21, 2014 8:45 AM
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Matt,

The modules are a bit confusing with respect to using just n or (n - 1) as some of the problems are mixed up and it depends on what you are given as to which to use.

I tell students that if we are starting with an initial quantity at n = 0 then we use n. Example if you have $5000 in a bank account growing at 5% per year, the explicit formula would be f(n) = 5000(1.05)^n since if we substitute 0 for n, we are left with our initial value of 5000.

When dealing with sequences (and some applications of functions), we start with some initial quantity when n = 1. This is when we use (n - 1). So if it's a geometric sequence with the first term of 5000 and common ratio of 1.05, it would look like f(n) = 5000(1.05)^(n-1) so when you substitute 1 in for n, 5000 comes out.

It's a bit confusing but all you really have to do is substitute a few values for n into the function to see if you get the values of f(n) you are looking for. Hope that helps......

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