Write a recursive rule and an explicit rule for the arithmetic sequence 19,9,-1,-

the formula is an =a1+d(n-1)

where a1 is the first terms

d is the common difference

a1= 19

d 1= 9-19 = -10

check: -1-9 = -10  the sequence goes down by 10

n  is the term number

an = 19 - 10(n-1)

we can distribute

an = 19 -10n +10

an = 29-10n

Check our work:

a4 = 29 - 10*4

    = 29 - 40

  = -11

the 4th term is -11 which 19,9,-1,-11,...  shows, so  we are good

an = 19 - 10(n-1)  or an = 29-10n

whole numbers.

step-by-step explanation:

we are given the average monthly rainfall (in millimeters) model r(m) for the years 1900-2009 as a function of the month number m.

as we can see m is taken for the number of months for years 1900-2009.

we know that number of months can't be a negative number or decimal number or a fraction.

so, the number of months could be only positive whole numbers.

therefore, whole numbers is more appropriate for the domain of r.