September 11, 2012Using Graphs and Linear Equations in Word Problems

Warm-up: 1. Sketch the graphsa) x2 + (y – 1)2 = 9 b)

2. Use the algebraic tests to check for symmetry to both axes and the origin: xy2 + 10 = 0

y x 3

HW 1.2-1.3 word problems: Pg. 23 #72, Pg. 36 #96, 106, 109Quiz 1.1: B Thursday, E Friday

Check HW 1.2

Using graphs and linear equations to solve word problems.

Depreciation:A manufacturing plant purchases a new molding

machine for $225,000. the depreciated value y (reduced value) after t years is given by

y = 225,000 – 20,000t, 0 ≤ t ≤ 6. Sketch the graph of the equation.

The graph shows the average salaries for high school principals from 1990 through 2002.

a) Use the slopes to determine the time periods in which the average salary increased the greatest and the least.

b) Find the slope of the line segment

connecting the years 1990 and 2002. c) Interpret the meaning of the slope in

part (b) in the context of the problem.

Using Slope in Word Problems

Using rate of change

The cash flow per share for the Timberland Co. was $0.18 in 1995 and $4.04 in 2003. Write a linear equation that gives the cash flow per share in terms of the year. Let t = 5 represent 1995. Then predict the cash flows for the years 2008 and 2010.