1



DISCOVERING SLOPE & SLOPE INTERCEPT FORM

This lesson is a review of slope. It will guide you through discovering slope-intercept form using paper/pencil and a graphing calculator. It includes looking at positive/negative slope, comparing the steepness of slopes, and relating slope to real-world applications (handicapped ramps, stairs).

a) Plot the points ( -1, -3) and (2,3) on the grid and then connect them.

b) Name the y-intercept as a coordinate.

c) Count blocks up and then right to move from ( -1, -3) to (2,3). Up is a positive direction; right is a positive direction. Write these results in rise/run (fraction) form.

d) You have just named the slope for this line. Is the slope rising or falling?

e) Now count blocks moving from (2,3) to (-1, -3), in other words, count blocks down and then left. Down is a negative direction (what sign should you then write before your number?); left is a negative direction (what sign should you then write before your number?). Write these results in rise/run (fraction) form. You have just named the slope for this line.

f) Now write your results in proportion form (setting the two fractions equal to one another). Is this a true statement? How so?

a) Plot the points ( -4, 2) and (5,-1) on the grid.

Thinking of what you did in Problems #1, name the slope of the drawn line. In other words, how did you get from one point to the other?

Is the slope positive (rising) or negative (falling)? Why?

Now go from the opposite point to the other. Name the slope.

Are the slopes equivalent? Why?

Slope is a fraction that tells you how steep a line is. The numerator tells you the vertical distance and the denominator tells you the horizontal distance. We describe slope as [pic] to help us remember this.

3. Complete the following table.

| |Original Equation |Rewrite as y= |x-intercept |y-intercept |Slope [pic] |

|a. |2y-4=x | |( , 0) |( 0 , ) | |

|b. |2y+6=10x | |( , 0) |( 0 , ) | |

|c. |2y+8=4x | |( , 0) |( 0 , ) | |

|d. |-y+3=x | |( , 0) |( 0 , ) | |

|e. |y-1=-4x | |( , 0) |( 0 , ) | |

|f. |4y-20=-x | |( , 0) |( 0 , ) | |

4. In each row, compare the slope and the numbers in the equation of the form “y=”. What do you notice?

5. In each row, compare the y-intercept and numbers in the equation of the form “y=”. What do you notice?

6. Make some conclusions about what you noticed in comparing slope and y-intercept with the equations written in “y=” form.

7. Extension questions:

a. Given the equation y = 2x + 5, where would the graph of this equation cross the y-axis? What is the slope of this line?

b. Graph the equation in part a on your calculator and compare your results to the graph.

c. Given the equation y = 5 + 2x, where would the graph of this equation cross the y-axis? What is the slope of this line?

d. Graph the equation in part c in your calculator on the same grid as part a.

e. How many lines do you have on your calculator?

f. What happened? Why did this happen?

g. What arithmetic property of real numbers have you just rediscovered? Give another example using this property. State the y-intercept and the slope. What can you conclude?

h. Given the equation y = 3x, where would the graph of this equation cross the y-axis? Why did you say what you wrote? Check your graph with the graphing calculator.

Equations in the form y=mx+b are equations in “slope-intercept form”, where m is the slope and b is the y-intercept.

8. Graph the equations a, b, and c from the chart in question 3 in your calculator and sketch the graphs below.

[pic] [pic] [pic]

9. What do all of the graphs in question 8 have in common? How does this relate to the slope?

10. What do you notice about how the slope relates to the steepness of the lines in question 8?

11. Graph equations d, e, and f from the chart in question 3 in your calculator and sketch below.

[pic] [pic] [pic]

12. What do all of the graphs in question 11 have in common? How does this relate to the slope?

13. What do you notice about how the slope relates to the steepness of the lines in question 11?

14. For each pair of equations, circle the equation of the line that would be steeper when graphed. If they have the same steepness, circle both of them.

[pic]

15. Rewrite each of the following equations in slope-intercept form; then match each equation to its graph.

1. x=y 2. -2y+10=x 3. 3y+3=2x

4. ¼ x=y-4 5. y+2x=1 6. y+x=1

CHECK FOR UNDERSTANDING:

a. In y=mx+b, m represents the ________________________ of the line.

b. In y=mx+b, b represents the _________________________ of the line.

c. Rise is the _________________________ distance.

d. Run is the _________________________ distance.

e. Create three equations in slope-intercept form.

y=_____________ y=___________ y=___________

f. Circle the slope in each equation.

g. Box the y-intercept in each equation.

h. Graph each equation in your calculator and sketch below.

[pic] [pic] [pic]

i. For each equation, name two points that are on each line, other than the y-intercept.

Equation #1:(_____,_____), (_____,_____)

Equation #2:(_____,_____), (_____,_____)

Equation #3:(_____,_____), (_____,_____)

j. Look at the table feature in your calculator to verify that your points are on the line.

k. Create two more equations. Circle the slope and box the y-intercept. Graph each equation in the calculator and sketch in the space below. Notice that graph paper has not been provided. (

EXTENSION:

The building codes and safety standards for slope are listed below:

| |Maximum Slope |

|Ramps-wheelchair |0.125 |

|Ramps-walking |0.3 |

|Driveway or street parking |0.22 |

|Stairs |0.83 |

1) Some streets in San Francisco are on hills with a run of 9 m and a rise of 4.2 m. Would it be safe to park your car on one of those streets?

2) The Kelly’s driveway has a run of 1.2 m and a rise of 0.4 m. Does it meet the safety specifications?

3) A ramp is to be built at the library for wheelchair accessibility. When a grid is placed over the architect’s plans, the top of the ramp has coordinates of (72m,4m). The bottom of the ramp has coordinates (22m,1m). Will the ramp meet safety specifications? Graph this situation on the graph paper provided.

EXTENSION 2:

A stairway is made up of a set of steps. Each steps consists of a step riser and a step tread.

1) A set of stairs is made up of a set of constructed with a step tread of 12 inches and a step riser of 6 inches. What is the slope of the stairway?

2) Measure the step tread and step riser for five stairways in PSH and two handicapped ramps. Then compute each slope. Record on the chart below.

|STAIRWAY |TREAD |RISER |SLOPE |

| | | | |

| | | | |

| | | | |

| | | | |

| | | | |

|RAMP |RISE |RUN |SLOPE |

| | | | |

| | | | |

3) Graph each slope on one graph with the y-intercept being (0,0) for all seven lines. First graph on calculator, then sketch below using a different color for each line. Compare slopes.

4) Which set of steps are the most comfortable to walk on?

5) Do our handicapped ramps meet the building specifications from the chart in the first extension?

Summarize all of the concepts that you learned in this lesson.

Name a real-world situation where slope can be useful (do not include any of the examples in the entire lesson).

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download