1. Warm- Up
Jerry wants to ride in a hot air balloon. It costs $180 dollars to rent the balloon and an additional $30 dollars for each hour the balloon is in the air. Jerry has $250 dollars. Will he be able to afford a two hour balloon ride?

2. Unit 6 Day 6
Point Slope Form

3. But what if we don’t know the y-intercept?!
Slope Intercept Form
Slope intercept form is a great way to write a linear equation if we know the slope and the y-intercept!
slope
y = mx + b
y-intercept
But what if we don’t know the y-intercept?!

4. y – y1 = m(x – x1) Point Slope Form!
It’s okay if we don’t know the y-intercept. All you need is:
the slope, m
a point on the line, (x1, y1)
Then, put them in the Point Slope Equation:
y – y1 = m(x – x1)

5. Example 1
y – y1 = m(x – x1)
Write an equation in point slope form for a line with a slope of 4 that includes the point (3, -2).

6. y – y1 = m(x – x1)
Example 2: Write an equation in point slope form for a line with a slope of -⅔ that includes the point (-5, 4).
Example 3: Write an equation in point slope form for a line with a slope of -2 that includes the point (7, 6).

7. Graphing In Point Slope Form
y – y1 = m(x – x1)
Use the formula to find (x1, y1). Then, plot the coordinate.
Use m, the slope, to make your line.
m = m =
rise
run

8. Example 4: Graph the Line1 2 4 3 5 -1 -2 -3 -4 -5
y – y1 = m(x – x1)
What is the point?
What is the slope?

9. Example 5: Graph the Line1 2 4 3 5 -1 -2 -3 -4 -5
y – y1 = m(x – x1)
What is the point?
What is the slope?

10. Choose the correct formula for each scenario.
Slope Intercept
y = mx + b
m is the slope
b is the y intercept
Write a an equation for a line with a slope of 5 and a y-intercept of -2.
Write an equation for a line that includes the point (-7, 3) with a slope of ⅘.
Write an equation for a line with a slope of -⅞ and includes the point (8, 6).
Write an equation for a line with a y-intercept of 7 and a slope of -3.
Point Slope
y – y1 = m(x – x1)
m is the slope
(x1, y1) is a point on the line