the annual household cost of telephone service in the US increased at a relatively constant rate of $27.80 per year from 1981 to 2001. in 2001 the annual household cost of telephone service was $914.

a: what was the annual household cost of telephone service in 1981?

b: write an equation that gives the annual household cost of telephone service as a function of the number of years since 1981.

c: find the household cost of telephone service 2000

Was there something confusing about the help posted here?

http://www.jiskha.com/display.cgi?id=1384483325

so is it 886.2

yes.

ok and then for the one that said find the household cost of telephone service in 2000

Well, since 886.2 = 914 - 27.80, that is the cost in 2000.

Now, if you want to find the cost in 1981, then you have to solve

x + 27.80*20 = 914

That is, we know the cost after 20 years (914), but we want to find out where it started.

a: To find the annual household cost of telephone service in 1981, we need to subtract the accumulated increase from the cost in 2001.

Since the annual household cost increased by $27.80 per year, we can calculate the number of years between 2001 and 1981 by taking 2001 - 1981 = 20 years.

Then, we multiply the 20 years by the yearly increase to find the accumulated increase over the years: 20 years × $27.80/year = $556.

Finally, we subtract this accumulated increase from the cost in 2001 to find the annual household cost in 1981: $914 - $556 = $358.

Therefore, the annual household cost of telephone service in 1981 was $358.

b: We can write the equation that gives the annual household cost of telephone service as a function of the number of years since 1981 as:

Cost(years) = $358 + ($27.80/year) × years

This equation takes the initial cost in 1981 ($358) and adds the accumulated increase based on the number of years since 1981.

c: To find the household cost of telephone service in 2000, we need to calculate the number of years between 2000 and 1981.

We can subtract 1981 from 2000 to find the number of years: 2000 - 1981 = 19 years.

Then, we plug this value into our equation:

Cost(19) = $358 + ($27.80/year) × 19

Calculating this expression gives us:

Cost(19) = $358 + $527.20 = $885.20

Therefore, the household cost of telephone service in 2000 was $885.20.