Exercise 121 Page 412

a We are given an explicit rule of a sequence and are asked to find the first 4 terms.

a_n=3 * 5^(n-1) To do so, we will construct a table.

The first 4 terms of this explicit sequence are 3, 15, 75, and 375.

b We are given a recursive rule of a sequence and are asked to find the first 4 terms.

a_1=10, a_(n+1)=- 5a_n To do so, we will construct a table.

n	a_(n+1)=- 5a_n	- 5a_n	a_(n+1)
0	a_1=10	-	10
1	a_2=- 5a_1	- 5 a_1=- 5( 10)	- 50
2	a_3=- 5a_2	- 5 a_2=- 5( - 50)	250
3	a_4=- 5a_3	- 5a_3=- 5(250)	- 1250

The first 4 terms of this explicit sequence are 10, - 50, 250, and - 1250.

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