1. Drill #23*
Find the equation of (in point- slope form) and graph the following linear functions:
1. Passing through the points (-1, -1) and (1, 3)
2. Passing through ( -1, 3) and parallel to
y = 2x + 2
3. Passing through ( 2, 3) and perpendicular to
y = - ½ x + 3

2. On the quiz Monday:
Find the equation of a line (in slope- intercept or point- slope form):
1. passing through 2 points.
2. parallel or perpendicular to a line passing through a point.
3. given the slope and a point
4. given the graph of the line
Graph a line given the equation in point- slope, slope-intercept, or standard form.

3. Writing Equations of Lines
1st Determine the slope of the line that we are writing the equation for.
If finding a parallel line use the same slope
If finding a perpendicular line use the negative reciprocal slope
2nd Find a point, any ordered pair (x, y) on the line.
3rd Determine what form you are going to use
If Slope- Intercept, substitute the slope for m and the point (x, y) for x and y into the equation y = mx + b and solve for b
If Point-Slope substitute the point and the slope m into the Point- Slope equation

4. To graph a line: If the equation is in point- slope form:
Determine (x 1 , y1) and plot the point
Use the slope m (rise over run) to get a second point
Draw a line between the points
If the equation is in slope- intercept form
Plot b (the y- intercept)
If the equation is in Standard form
Find and plot the x- and y- intercepts

5. Find the equation of the line (#23*)
In point- slope and slope- intercept form
4. Passing through (2, -1) with m = 3.
5. Passing through (-2, -4) with m = ½

6. Find the equation of the following:
6. Hint: Use the slope (m) and y- intercept (b). 3 x -2 y

7. Classwork (#23*) Graph the following linear equations:
7. y – 3 = ½ (x + 1) (pt- slope)
8. y = - ¼ x + 3 (slope intercept)
9. 3x - 2y = 9 (standard)

8. Prediction Equation **(27.)
Definition: The prediction equation can be found using two points from the line of best fit (they do not have to be data points)
The prediction equation can be used to estimate the value of one of the variables given the other.

9. Equation of the line of best-fit
Find two points on the line: (7, 6) and (1, 0)
Find the slope:
m = 1
Substitute m and find b:
y = 1x + b
Substitute (1, 0) or (7, 6)
0 = 1(1) + b
-1 = b
y = 1x - 1

10. Slope… What does the slope mean? What are the units?
The slope means that the _____________ is
y - unit
_____________ by _____________
inc. / dec. slope
every ______________
x - unit

11. Example 2 Exp 9 4 3 1 10 6 12 8 Rate $17 $10 $7 $6 $12 $20 $15
Make a scatter plot of the following data.
Draw a line of best fit.
3. Write an equation for the line of best fit relating the rate of pay (y) to the years of experience (x)
Exp 9 4 3 1 10 6 12 8
Rate
$17
$10 $7 $6
$12
$20
$15

12. To find the equation of the line of best fit
Find two points on your line (they do not have to be data points)
Find the slope between the two points (using the slope formula)
Use a point and the slope and write your equation in point slope form.
Get your equation into slope intercept form by solving for y