# Thread: Need help with Linear functions

1. ## Need help with Linear functions

How am I suppose to solve this problem? By creating a formula for it?

If so this is what I got so far; by taking the years 1980-1990, I tried to find the average rate of change of the population, 17.2 - 14.9/1990 - 1980, which came out to be 0.23. After that I tried writing up a formula for it by using y = mx + b. So it would be P = 0.23x + 17.2. After that in order to find what is the population in 1988 do I just put in an 8 in that equation?
P = 0.23(8) + 17.2 = 19.04?

Here is the question:

2. Originally Posted by nox16
How am I suppose to solve this problem? By creating a formula for it?

If so this is what I got so far; by taking the years 1980-1990, I tried to find the average rate of change of the population, 17.2 - 14.9/1990 - 1980, which came out to be 0.23. After that I tried writing up a formula for it by using y = mx + b. So it would be P = 0.23x + 17.2. After that in order to find what is the population in 1988 do I just put in an 8 in that equation?
P = 0.23(8) + 17.2 = 19.04?
You probably have noticed that the population in 1988 is much greater/larger(?) than in 1990.

1. Let x denote the numbers of years from 1980.

2. Using the interval from 1980 to 1990 you'll get m = 0.23

3. If you use the endpoints of the interval to determine the population :

$P= 14.9 + ( 0.23 \cdot x )$

4. Now plug in x = 8 .