1. Graphing a Linear Function (Line)
There are two formulas to use for graphing a line:
Formula 1:
y = mx + b
m is the slope (how the line “moves”)
b is the y intercept (where the line “begins” on the y axis)
This formula is used about 2/3 of the time in 9th grade algebra
Formula 2:
y – y1 = m(x – x1)
(x1, y1) is any point that appears on the line
This formula is used when the question does not provide a
y-intercept (b) value

2. Graphing a Linear Function (Line)
What if we don't know the slope?
Find it!!
Option 1 – Use the two given points to find the slope using slope formula
y2 – y1
x2 – x1
Option 2 – Get the line into y = mx + b format and determine “m”

3. Graphing a Linear Function (Line)
Finding Intercepts:
Finding a “y” intercept:
Using the given equation, plug in zero for the “x” value and solve for y
Finding an “x” intercept:
Using the given equation, plug in zero for the “y” value and solve for x

4. Graphing a Linear Function (Line)
Take the equation:
y = 2x – 5
b value = -5
start at -5 on the y axis
m value = 2 Express as 2/1.
slope of 2/1 makes the graph move up 2 to the right 1
Example Question:
Is the point (3,1) on the graph of y = 2x – 5?

5. Graphing a Linear Function (Line)
Next Take the equation:
y = -4x + 3
Find b and m values
Graph the line
Decide if the point (-1, 6) is on this graph

6. Graphing a Linear Function (Line)
What to do when the graph doesn’t help you?
y = 5x - 2
Find b and m values
Graph the line
Determine if the point (20, 98) is on this line
Now we have to use some algebra
(20,98) is a possible point on this line
20 is the x value, 98 is the y value.
Plug in to find the b value. If b value matches, then this point is on the line.

7. Graphing a Linear Function (Line)
Example 2:
y = -2x 3
Does the point (30, 27) appear on this line?