2.1.3 Algebra 1 Lesson

In Lesson 2.1.2, you used the dimensions of a slope triangle to measure the steepness of a line.  Today you will use the idea of stairs to understand slope even better.  You will review the difference between positive and negative slopes and will draw a line when given information about Δx and Δy.

​

During the lesson, ask your teammates the following focus questions:

How can you tell if the slope is positive or negative?

What makes a line steeper?  What makes a line less steep?

What does a line with a slope of zero look like?

Picture yourself climbing (or descending) the stairs from left to right on each of the lines on the graph. Write down the slope (rise/run) for each line on the graph; make sure to label which line has each slope.

Multiple Choice

Which is the steepest?

• A

• B

• C

• D

Multiple Choice

Which is the least steep?

• A

• B

• C

• D

​Answers

​

Line A slope = 1/1 = 1

​Line B slope = 3/1 = 3 (steepest)

​Line C slope = 1/2

​Line D slope = -2/5 (least steep)

Multiple Choice

Which is steeper, line B or line C?

• B

• C

Multiple Choice

Which line is the steepest?

• A

• B

• C

• D

• E

Multiple Choice

What is the slope of line D?

• 1/5

• 5/1

• -1/5

• -5/1

Multiple Choice

What is the slope of line E?

• 0

• 1

• -1

• undefined

Multiple Choice

Which line would be steeper?

• slope = -3/5

• slope = -5/3

​On the next slide you will be asked to graph lines. Here are two examples of graphing lines. You can start by plotting the y-intercept and then use the slope to add more points.

​Sketch a graph of each line in your notes.

Do not move on until all 4 have been graphed.

Multiple Choice

From your graphs in the previous slide, describe the graph of part d.

• Positive sloped line

• Horizontal line

• Vertical line

• Negative sloped line

​Answers to graphing lines a-d

Multiple Choice

Which of the lines was NOT a function?

*function: each input has only one output

• a

• b

• c

• d

Multiple Choice

Does it matter which slope triangle you use to find the slope of the line?

• Yes

• No

Multiple Choice

What is the slope of the line?

• 1/2

• 2/1

• 4/3

• 3/4

Multiple Choice

In your notes write down:

Slope intercept form of a line: y = mx + b

m is the slope and b is the _______

• y-intercept

• x-intercept

• steepness

• banana