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# The slope-intercept form of a line: y = mx + b

The slope-intercept form of a line: y = mx + b. Graph the following family of lines using the graphing calculator:. y = 3x + 2 y = 5x + 2 y = -4 x + 2 y = 1/2 x + 2 All of these equations are written in y = mx+b form. What does m represent in each equation?

## The slope-intercept form of a line: y = mx + b

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1. The slope-intercept form of a line:y = mx + b

2. Graph the following family of lines using the graphing calculator: • y = 3x + 2 • y = 5x + 2 • y = -4 x + 2 • y = 1/2 x + 2 All of these equations are written in y = mx+b form. What does m represent in each equation? Check your hypothesis by using the table feature of the calculator.

3. Graph the following family of lines using the graphing calculator: • y = 3x + 2 • y = 3x - 4 • y = 3x • y = 3 x + 8 All of these equations are written in y = mx+b form. What does b represent in each equation? Check your hypothesis by using the table feature of the calculator.

4. Given y = mx + b • m represents the slope of the line • b represents the y-intercept -- the point where the line intercepts or crosses the y-axis.

5. Graphing lines in the form y = mx + b is very easy since you know one point, the y-intercept, and the slope. Graph each of the following: • y = 2x + 5 • y = - x – 3 • y = 4x • y = - 2

6. Finding the equations of lines is very easy if you know the y-intercept and slope. Find the equation of the line: • that passes through the origin with slope – 2. • with y–intercept of 4 and slope 2/3. • that is horizontal and passes through the point ( 2, 5)

7. What if the equation is not given in y = mx + b form? Graph the equation whose standard form is 3x + 2y = 6. • Strategy 1: Rewrite the equation in y = mx + b form. • Strategy 2: Find the x-intercept and the y-intercept.

8. To find the x-intercept and the y-intercept of a line written in standard form: • Let x = 0 to find the y-intercept. • Let y = 0 to find the x-intercept. • Example: Find the x-intercept and the y-intercept of the line 3x – 5y = 15. Then graph the line.

9. Graphing equations in different forms: • Point-slope form: y – y1 = m(x – x1) Use a point (x1, y1 ) and the slope, m. • Standard form Ax + By = C • Rewrite in y = mx + b form OR • Find the x-intercept and the y-intercept OR • Make a table of solutions. • Slope-intercept form y = mx + b Use the y-intercept and the slope.

10. Assignment: • 6.4 #19-45 odds Due Wednesday 1/14/04 • 6.5 #13-25 all. Use graph paper. Write the equation next to each graph. Due Thursday 1/15/05

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