Welcome! September 20 , 2010

# Welcome! September 20 , 2010

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## Welcome! September 20 , 2010

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##### Presentation Transcript

1. Welcome!September 20, 2010 Take out: Pencil & journal Homework: • Objectives: • Students will determine the relationship between points and slope • Students will explore how scale changes a graph • Students will discover how to write the equation for a line Do Now: • Do Now • Do work in your Notes When you are done writing, put your pencil down and silently look up. Agenda: • Do Now • HW Check • Intro to Slope Formula • Modeling Problem • Work on class activity • Ticket to Go

2. (4, 1) (-2, -2) Assuming each line is one unit, how many ways can we find the slope of this line?

3. Could these two lines have the same slope? How? Complete in pairs p30, psD #1 (10 minutes)

4. Graph and find the slope given the points 1. (-3, 4) and (-7, 2) 2. (2, 4) and (3, 3) 3. (3, 5) and (4, 5) 4. (-3, 4) and (-4, 6) Two of the lines have negative slope, what do you notice about these lines? One of the lines has a slope of 0. What do you notice about that line? IS THERE A BETTER WAY TO FIND SLOPE???

5. FORMULA FOR FINDING SLOPE The formula is used when you know two points of a line. EXAMPLE

6. Find the slope of the line between the two points (-4, 8) and (10, -4) If it helps label the points. Then use the formula

7. Vocabulary The equation for a line is often written in the form: y = mx + b, where m = slope and b = y-intercept. This is called Slope-Intercept form. Coefficient The multiplier of a variable Example: y = 2x + 3, 2 is the coefficient of x y-intercept The y-coordinate of the point at which the line crosses (or intercepts) the y-axis What is the y-intercept for y = 2x + 3? How about y = 3x - 4? How do you know?

8. Write the Equation If a line has a slope of 3 and passes through the point (2, 5). Since slope = 3, we can replace m in y=mx+b with y=3x+b Now, replace x and y with 2 and 5, respectively giving you 5=3(2) + b Simplify, and you get b = -1 So, the equation for the line is: y = 3x -1

9. Find the line using the given Slope 4 and passes through (1, 5) Slope -2 and passes through (8, -12) Slope 0 and passes through (3, 5) If you finish early, graph each equation.

10. Here’s a Challenge! How could you find the equation for a line using just two points? Try with the following points (3, 7) and (8, 12) (6, 11) and (18, 17) (0, 0) and (100, 100) (3, 5) and (-1, 5)

11. Ticket to GO! Find the equation for the line with slope 2/3 that passes through the point (9, 9)