Big Ideas Math Integrated I, 2016
BI
Big Ideas Math Integrated I, 2016 View details
6. Recursively Defined Sequences
Continue to next subchapter

Exercise 13 Page 316

Can you find the common ratio and the first term just by looking at the explicit formula?

a_n=4a_(n-1); a_1 = - 2.5

Practice makes perfect
The explicit formula of a geometric sequence combines the information provided by the two equations of the recursive form into a single equation. Recursive:& a_n= r* a_(n-1); a_1= a_1 Explicit:& a_n= a_1 r^(n-1)

In these formulas, r is the common ratio and a_1 is the first term. Looking at the given explicit formula, we can identify the common ratio r and the value of the first term a_1. a_n= -2.5( 4)^(n-1) We can see that 4 is the common ratio and the first term is - 2.5. Now we have enough information to form an explicit formula for this sequence. a_n&= 4a_(n-1); a_1&= - 2.5