Big Ideas Math Algebra 2, 2014
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Big Ideas Math Algebra 2, 2014 View details
5. Using Recursive Rules with Sequences
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Exercise 46 Page 448

Is it possible to find the common ratio and the first term just by looking at the recursive rule?

a_n=- 4(0.65)^(n-1)

Practice makes perfect
The explicit rule of a geometric sequence combines the information provided by the two equations of the recursive rule into a single equation. Recursive:& a_1= a_1, a_n= r* a_(n-1) Explicit:& a_n= a_1 r^(n-1)In these rules, r is the common ratio and a_1 is the first term. Looking at the given recursive rule, we can identify the common ratio r and the value of the first term a_1. a_1= - 4, a_n= 0.65a_(n-1) We can see that 0.65 is the common ratio and the first term is - 4. Now we have enough information to form an explicit rule for this sequence.
a_n=a_1r^(n-1)
a_n= - 4( 0.65)^(n-1)