1. The Slope-Intercept Formula
Solving an equation for “y”

2. The Slope-Intercept Formula
When you solve an equation for “y”
You are putting the equation in “slope-intercept form”

3. Let’s look at the formula and it’s parts.
Represents the y - intercept
Represents the numerical value for the SLOPE of the line
This is where the line will cross the y-axis.
The x and y come from a set of ordered pairs (x, y). We use this when writing linear equations.

4. Why do we need this formula?
We use this formula to WRITE and GRAPH linear equations.

5. Solve for Y We want y by itself
Can’t add or sub these
Why?
They are not
Like Terms
We want y by itself
Move the x term (do the opposite + or -)
Move the term in front of y (do the opposite x or )
Slope = ½
Y-intercept = -2
write it as (0, -2)

6. Write these equations in slope-intercept form.
To solve for “y” you have to get the “y” by itself.
Use opposite operations to move everything away from the “y”
1st – Mark the variable you are solving for then leave it alone!!
Next – Use opposite operations to move everything away from the “y”.
You can’t add –x and 8, so just bring them down.
Now divide everything by -2.
Y - intercept = ________
Slope = _____________

7. Write in slope-intercept form then name the slope (m) and y-intercept (b).
m=_____ b=_____
m=_____ b=_____
m=_____ b=_____

8. Write in slope-intercept form then name the slope (m) and y-intercept (b).
Zero slope and No Slope
These are special equations. When you only see one variable, that means the line only touches one axis.
Therefore the slope will either be:
1. Zero (0) or No Slope
These
Equations
Only have
A “y” so
They only
Touch the
“y” axis and
Form
Horizontal
Lines.
Their slope
Is ZERO
These
Equations
Only have
An “x” so
They only
Touch the
“x” axis and
Form
Vertical
Lines.
Their’s Is
UNDEFINED

9. Now let’s use the formula to WRITE an equation.
Write an equation in slope-intercept form when given the slope and the y-intercept.
m = 3, b = 1
Simply replace the “m” and the “b” in the formula with the numbers and you have an equation.

10. Writing Slope-Intercept Equations - Examples
Write an equation in slope-intercept form when given the slope and the y-intercept.
m = ½ , b = 1
m = -3, b = 5
m = 4, b = -2
m = 0, b = 7