1. HPC 2.2 – Linear Functions & Models Learning Targets: -Graph linear functions. -Draw and interpret scatter diagrams. -Distinguish between linear and nonlinear relations. -Use your calculator to find the line of best fit. -Construct a linear model using direct variation.

2. What is a linear function? A function of the form Graph is a straight line x is the independent variable; y = f(x) is the dependent variable.

3. DIRECT VARIATION Let x and y denote two quantities. Then y varies directly with x, or y is directly proportional to x, if there is a nonzero number k such that y = kx. k is called the constant of proportionality. If y varies directly with x, then y is a linear function of x.

4. Ex 1) Suppose that a company has just purchased a new machine for its manufacturing facility for $120,000. The company chooses to depreciate the machine using the straight-line method over 10 years. a)Write a linear function that expresses the book value of the machine as a function of its age. b)Graph the linear function. c)What is the book value of the machine after 4 years?

5. Ex 2) a) Draw a scatter diagram (a.k.a. scatterplot). b)Select two points from the scatter diagram and find the equation of the line containing the points selected. c)Graph the line found in part b on the scatter diagram. d)Use a graphing utility to find the line of best fit. e)Use a graphing utility to graph the line of best fit on the scatter diagram. x35791113 y0236911

6. Ex 3) The amount of money that a lending institution will allow you to borrow mainly depends on the interest rate and your annual income. The following data represent the annual income, I, required by a bank in order to lend L dollars at an interest rate of 7.5% for 30 years. Annual Income, I ($)Loan Amount, L ($) 15,00044,600 20,00059,500 25,00074,500 30,00089,400 35,000104,300 40,000119,200 45,000134,100 50,000149,000 55,000163,900 60,000178,800 65,000193,700 70,000208,600

7. Ex 3) continued… a)Which is the independent variable? Dependent variable? b)Use a graphing utility to draw a scatter diagram of the data. c)Use a graphing utility to find the line of best fit to the data. d)Graph the line of best fit on the scatter diagram drawn in part b. e)Interpret the slope of the line of best fit. f) Determine the loan amount that an individual would quality for if her income is $42,000. _________________

8. Ex 4) The monthly payment p on a mortgage varies directly with the amount borrowed B. If the monthly payment on a 15-year mortgage is $8.99 for every $1,000 borrowed, find a linear function that relates the monthly payment p to the amount borrowed B for a mortgage with the same terms. Then find the monthly payment when the amount borrowed is $175,000.