1. (For help, go to Lessons 1-6 and 2-6.) ALGEBRA 1 LESSON 6-2 Slope-Intercept Form 8-4 Evaluate each expression. 1. 6a + 3 for a = 22. –2x – 5 for x = 3 3. x + 2 for x = 164. 0.2x + 2 for x = 15 Solve each equation for y. 5. y – 5 = 4x6. y + 2x = 7 7. 2y + 6 = –8x 1414

2. Slope-Intercept Form 1. 6a + 3 for a = 2: 6(2) + 3 = 12 + 3 = 15 2. –2x – 5 for x = 3: –2(3) – 5 = –6 – 5 = –11 3. x + 2 for x = 16: (16) + 2 = 4 + 2 = 6 4. 0.2x + 2 for x = 15: 0.2(15) + 2 = 3 + 2 = 5 5. y – 5 = 4x 6. y + 2x = 7 y – 5 + 5 = 4x + 5 y + 2x – 2x = 7 – 2x y = 4x + 5 y = –2x + 7 7. 2y + 6 = –8x 2y + 6 – 6 = –8x – 6 2y = –8x – 6 = y = –4x – 3 – 8x – 6 2 ALGEBRA 1 LESSON 6-2 Solutions 8-4 1414 1414 2y y

3. Slope-Intercept Form The slope is 2; the y-intercept is –3. What are the slope and y-intercept of y = 2x – 3? mx + b = 2x – 3 = Use the Slope-Intercept form. ALGEBRA 1 LESSON 6-2 8-4

4. 2525 Use the slope-intercept form. Substitute for m and 4 for b. y = mx + b y = x + 4 2525 Slope-Intercept Form Write an equation of the line with slope and y-intercept 4. ALGEBRA 1 LESSON 6-2 8-4 2525

5. Slope-Intercept Form 2323 y = mx + b y = – x + 1 Substitute – for m and 1 for b. 2323 Step 2 Write an equation in slope– intercept form. The y-intercept is 1. Write an equation for the line. Step 1 Find the slope. Two points on the line are (0, 1) and (3, –1). –1 – 1 3 – 0 slope = = – 2323 ALGEBRA 1 LESSON 6-2 8-4

6. Step 2 The slope is. Use slope to plot a second point. 1313 Slope-Intercept Form Step 1 The y-intercept is –2. So plot a point at (0,–2). Step 3 Draw a line through the two points. ALGEBRA 1 LESSON 6-2 Graph y = x – 2. 1313 8-4

7. Slope-Intercept Form The base pay for a used car salesperson is $300 per week. The salesperson also earns 15% commission on sales made. The equation t = 300 + 0.15s relates total earnings t to sales s. Graph the equations. ALGEBRA 1 LESSON 6-2 8-4 Step 1 Identify the slope and y-intercept. t = 300 + 0.15s t = 0.15s + 300 Rewrite the equation in slope intercept form. slope y-intercept

8. Step 2 Plot two points. First plot a point at the y-intercept. Then use the slope to plot a second point. The slope is 0.15, which equals. Plot a second point 15 units above and 100 units to the right of the y-intercept. Slope-Intercept Form (continued) Step 3 Draw a line through the points. ALGEBRA 1 LESSON 6-2 8-4 15 100

9. Slope-Intercept Form 5. Write an equation for the line. 6. Graph y = –x + 3. m = ; b = –3 3434 m = –2; b = 0 y = – x – 4 3535 y = 0.5x + 1 y = x – 3 1212 ALGEBRA 1 LESSON 6-2 8-4 Find the slope and y-intercept of each equation. 1. y = x – 3 2. y = –2x Write an equation of a line with the given slope and y-intercept. 3. m = –, b = –4 4. m = 0.5, b = 1 3434 3535