In 1990 the average family income was about 37000 and in 200

In 1990, the average family income was about $37000, and in 2005, it was about $60000. What is the average rate of change of family income per year? Recent, the population density D (in people per square mile) of the unites state could be described by D(t) = .581t + 21.5, where t is the time in year since 1990. What is the slope of the matching graph? Interpret the slope as a rate of change. State the domain of the following function f(x) = 5x + 120 g(x) = Squareroot 3x - 15 h(x) =7/2x - 8 State the domain and range of the following function f(x), using interval notation use the picture to evaluate f(3)

Solution

1) 1990 --- $ 37000 ; 2005--- $ 60,000

Average rate of change of family income per year = ( 60,000 - 37000)/( 2005 - 1990)

= 23000/15 = 1533.33 $ per year

2) D(t) = 0.581t + 21.5

t is the time since 1990.

Slope = 0.581 (+ve)

It means positive change in population density per year since 1990