Quick Graphing Using Slope-Intercept Form

1
4.5

• Quick Graphing Using Slope-Intercept Form

2
What are the different methods we have used to
graph a line?

• Plot points

• Make a table

• Find the x and y- intercepts

• Special horizontal and vertical lines

3
Slope-intercept form linear equation
y mxb
m represents the slope of the line
b represents the y-intercept where
the line crosses the y-axis
4
y mx b
You can tell by looking at the equation not only
where the line crosses y, but whether it has a
positive or negative slope. If m is positive the
slope is positive, and your line will go up from
left to right. If m is negative, the slope is
negative and your line will go down from left to
right.
5
Determine what is the slope, y-intercept, and
direction of each equation.

1. Slope 3 y-intercept 4goes up left to right
2. Slope ½ y-intercept -9 goes up left to
   right
3. Slope -4/5 y-intercept 7 goes down left to
   right
4. Slope -2 y-intercept -4 goes down left to
   right

1. y 3x 4
2. y ½ x 9
3. y -4/5 x 7
4. y -2x - 4

6
When your equation is not in slope intercept
form, rewrite it into slope-intercept form
(ymxb). 2x 5y - 10

• 2x 5y-10-5y -5y
• 2x 5y -10-2x -2x
• -5y -2x 10-5 -5 -5
• y 2/5x 2

What is the y- intercept?
2
What is the slope?
2/5
What direction will the line go?
Up, from left to right.
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Graph the line y 2/5x 2The slope is 2/5
the y-intercept is 2.

• Steps to graphing a line in slope intercept form
• Plot the y-intercept. (0,2)
• Count up 2 over 5 and plot next point.
• Connect the dots.

4
3
2
1
-4
-3
-2
1 2 3 4 5 6
-1
-1
-2
-3
-4
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Graph the line 2y -2x 6

1. Change to slope intercept form.
2. y -x 3
3. Y-intercept (0, 3)
4. Slope -1
5. Line will go down from left to right.

4
3
2
1
-4
-3
-2
1 2 3 4 5 6
-1
-1
-2
-3
-4
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Special line

• Parallel Lines lines have the same slope, but
  different y-intercept (b value)
• y 2x 4 and y 2x 3 are parallel lines.

10
Graph y -x6 and y -x2 on the same graph.
Notice that they each have the same slope of -1,
but they cross y at different spots.
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y -x 6
y -x 2