Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide 1
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide 2 Graphs of Linear Equations and Inequalities; Functions Chapter 3
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Objectives 1.Write an equation of a line given its slope and y- intercept. 2.Graph a line given its slope and a point on the line. 3.Write an equation of a line given its slope and any point on the line. 4.Write an equation of a line given two points on the line. 5.Write an equation of a line parallel or perpendicular to a given line. 6.Write an equation of a line that models real data.
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide 5 Write an equation of a line given slope and y-intercept. 3.4 Equations of Lines
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Example 1 Write an equation of the line with slope 2/3 and y- intercept (0, 1). Write an equation of a line given slope and y-intercept.
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Graph a line given its slope and a point on the line.
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Example 2 Graph 2x – 3y = 3 by using the slope and y-intercept. (continued) Graph a line given its slope and a point on the line.
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Example 2 Graph 2x – 3y = 3 by using the slope and y-intercept. (continued) Graph a line given its slope and a point on the line.
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Example 2 Graph 2x – 3y = 3 by using the slope and y-intercept. Graph a line given its slope and a point on the line.
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Example 4 Write an equation, in slope-intercept form, of the line having slope 4 passing through (2, 5). Write an equation of a line given its slope and any point on the line. Substitute x = 2, y = 5 and the given slope m = 4 into y = mx + b and solve for b.
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Write an equation of a line given its slope and any point on the line.
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Example 5b Write an equation of the line through (4, 2), with slope 3/5. Give the final answer in slope-intercept form. Write an equation of a line given its slope and any point on the line.
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Example 6 Write an equation of the line through the points ( 2, 5) and (3, 4). Give the final answer in slope-intercept form. Write an equation of a line given two points on the line. Now use either point and the point-slope form. Using (3, 4) gives (continued)
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Example 6 Write an equation of the line through the points ( 2, 5) and (3, 4). Give the final answer in slope-intercept form. Write an equation of a line given two points on the line.
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Write an equation of a line given two points on the line. Ax + By = C, called standard form, where A, B, and C are real numbers and A and B are not both 0. In most cases, A, B, and C are rational numbers.
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Example 7a Find the equation in slope-intercept form passing through the point ( 4, 5) and (a) parallel to the line 2x + 3y = 6; (b) perpendicular to the line 2x + 3y = 6. Write an equation of a line parallel or perpendicular to a given line. Find the slope of the line 2x + 3y = 6. (continued)
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Example 7a Find the equation in slope-intercept form passing through the point ( 4, 5) and parallel to the line 2x + 3y = 6 Write an equation of a line parallel or perpendicular to a given line. Parallel lines have the same slope. Use the point-slope form. (continued)
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Example 7a Find the equation in slope-intercept form passing through the point ( 4, 5) and parallel to the line 2x + 3y = 6 Write an equation of a line parallel or perpendicular to a given line.
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Example 7b Find the equation in slope-intercept form passing through the point ( 4, 5) and perpendicular to the line 2x + 3y = 6. Write an equation of a line parallel or perpendicular to a given line. The slope of the line is –2/3. A line that is perpendicular must have a slope that is the negative reciprocal or 3/2.
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Example 8a It is time to fill your car with gasoline. Gas is selling for $4.50 per gallon. Write an equation that describes the cost y to buy x gallons of gas. Write an equation of a line that models real data.
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Example 8b You can also get a car wash at the gas station if you pay an additional $3.00. Write an equation that defines the price for gas and a car wash. Write an equation of a line that models real data. Since an additional $3.00 will be charged, you pay $4.50x dollars for x gallons of gas and a car wash.
Copyright © 2010 Pearson Education, Inc. All rights reserved. 3.4 – Slide Equations of Lines Example 8c Interpret the ordered pairs (5, 25.5) and (10, 48) in relation to the equation from part b. Write an equation of a line that models real data. The ordered pair (5, 25.5) indicates that the price of 5 gal of gas and a car wash is $ Similarly, (10, 48) indicates that the price of 10 gal of gas and a car wash is $48.00.