1. Quick Graphing Using Slope-Intercept Form
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 = mx+b
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.
Slope = 3 y-intercept = 4 goes up left to right
Slope = ½ y-intercept = -9 goes up left to right
Slope = -4/5 y-intercept = 7 goes down left to right
Slope = -2 y-intercept = -4 goes down left to right
y = 3x + 4
y = ½ x – 9
y = -4/5 x + 7
y = -2x - 4

6. What is the y- intercept? What direction will the line go?
When your equation is not in slope intercept form, rewrite it into slope-intercept form (y=mx+b). 2x = 5y - 10
2x = 5y-10 -5y -5y
2x – 5y = x x
-5y = -2x –
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.

7. Graph the line y = 2/5x + 2 The 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 -1 -2 -3 -4

8. Graph the line 2y = -2x + 6 Change to slope intercept form. y = -x + 3
Y-intercept (0, 3)
Slope -1
Line will go down from left to right. 4 3 2 1 -4 -3 -2 -1 -1 -2 -3 -4

9. 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 = -x+6 and y = -x+2 on the same graph.
Notice that they each have the same slope of -1, but they cross y at different spots.

11. y = -x + 6
y = -x + 2