In 1990, the life expectancy of males in a certain country was 72.4 years. In 1994, it was 75.8 years...?

Question

Let E represent the life expectancy in year t and let t represent the number of years since 1990.
The linear function E(t) that fits the data is
E(t)=__t + ___. (round to the nearest tenth)

Use the function to predict the life expenctancy of males in 2008.
E(18)=___. (round to the nearest tenth)

Answer 1

basically you are asked to find the linear function E(t)
given two points, (0,72.4) and (4,75.8)

slope = (75.8-72.4)/(4-0) = .85

so E(t) = .85t + b (compare with y = mx + b)
sub in (0,72.4) to solve for b

then evaluate E(18) by subbing in t = 18