Question

Write an explicit formula fo the sequence 7,2,-3,-8,-13.... Then find the 14th term

(please explain)

Answer 1

The 14th term is -58

Explanation:

The formula for an arithmetic sequence is

an = a1+d(n-1)

where a1 is the first term

d is the common difference and

n is the term number

a1 = 7

d = 2-7 = -5

Check -3-2 = -5 so d = -5

an = 7 -5(n-1)

We want the 14th term

a14 = 7 -5(14-1)

a14 = 7 -5(13)

a14 = 7 -65

a14 = -58