SOLUTION: in 1990, the life expectancy of males in a certain country was 72.4 years. In 1994, it was 74.9 years. Let E represent the life expectancy in year t and let t represent the number

Algebra ->  Coordinate-system -> SOLUTION: in 1990, the life expectancy of males in a certain country was 72.4 years. In 1994, it was 74.9 years. Let E represent the life expectancy in year t and let t represent the number       Log On


   

Question 169536: in 1990, the life expectancy of males in a certain country was 72.4 years. In 1994, it was 74.9 years. Let E represent the life expectancy in year t and let t represent the number of years since 1990.
The linear expression E(t) that fits the data is E(t)=_______.
E(18) = _____.
Answer by Edwin McCravy(20086) About Me  (Show Source):
You can put this solution on YOUR website!

First let y represent the life expectancy and let x 
represent the number of years since 1990.  Then later 
we'll replace y by E(t) and x by t.

Then when x=0, then y=72.4, and
     when x=4, then y=74.9

So the problem now becomes:

Find the equation of the line which contains the points
(0,72.4) and (4,74.9).

Use the slope formula:

  

Use the point-slope form:

y-y%5B1%5D=m%28x-x%5B1%5D%29
y-72.4=.625%28x-0%29
y-72.4=.625x
y=.625x%2B72.4

Now replace y by E%28t%29 and x by t

E%28t%29=.625t%2B72.4

To find the life expectancy after 18 years from 1990.

E%2818%29=.625%2818%29%2B72.4=83.25

Since 18 years from 1990 is this year 2008, then if that
formula is a correct predictor, then the life expectancy
at present should be 83%261%2F4 years.

Maybe it'll be over 100 years by the time you get old!

Edwin