Exercise 13 Page 287

To find certain terms in a sequence described by an explicit formula, substitute the number of the desired term into the formula to get the term's value. For the given explicit formula, A(n)=2+(n-1)(- 2.5),we can find the second, fourth, and eleventh terms of the sequence by substituting 2, 4, and 11 into the formula for n.

A(n)=2+(n-1)(- 2.5)

Substitute

n= 2

A( 2)=2+( 2-1)(- 2.5)

SubTerm

Subtract term

A(2)=2+(1) (- 2.5)

IdPropMult

Identity Property of Multiplication

A(2)=2+(- 2.5)

AddNeg

a+(- b)=a-b

A(2)=2-2.5

SubTerm

Subtract term

A(2)=- 0.5

Now, let's do the same thing for the fourth and eleventh terms.

n^(th) term	2+(n-1)(- 2.5)	A(n)
2	2+( 2-1)(- 2.5)	- 0.5
4	2+( 4-1)(- 2.5)	- 5.5
11	2+( 11-1)(- 2.5)	- 23

The second, fourth, and eleventh terms are - 0.5, - 5.5, and - 23.