1. Warm Up for 9.6
Find the distance and midpointbetween the following sets of points.
(5, 19) and (-3, -1)
(7, -16) and (-2, -1)
(1, -4) and (0, 0)
(-6, 4) and (5, 20)
Answers: distance
Answers: midpoint
(1,9)
(5/2, -15/2)
(-1/2, -2)
(-1/2, 12)

2. Slope: algebra review #4
What is slope?
The steepness of a line.
What is the slope formula?
Slope =

3. Example 1 and 2: Find the slope between the two points.
a. ( 7,6) and (3,1)
Plug the numbers into the slope formula and simplify
b. ( -3, -15) and ( -5, 1)
Plug the numbers into the slope formula and simplify
Watch out for
DOUBLE NEGATIVES!

4. Last two examples: Example 3: find the slope of (7, 8) and (7, 5)
undefined
Plot the points and connect. “SLICES” through
the x-axis at 7
You can not have zero in the denominator so if you do the answer is “undefined”
x=7
The graph of a line with a undefined slope will be a vertical line. x y

5. Example 4: Find the slope of (5,9) and (-3,9)
Plot the points and
connect. “SLICES”
through the y-axis at 9
When zero is in the numerator the answer is just zero.
y=9 x
The graph of a line with zero slope is a horizontal line y

6. Parallel and Perpendicular Lines
Lines that are parallel have
_____________________________.
Lines that are perpendicular have
____________________________.
the same slope
opposite reciprocal slopes
This means opposite signs and the fractions are flipped.

7. Discovering Parallel Lines
Predict which of the following will be parallel.
y = ½x + 1
y = -3x – 4
y = ½x – 4
y = -½x + 1
1 and 2 since the slopes
are the same.

8. Discovering Perpendicular Lines
Predict which lines will be perpendicular, explain your reasoning.
y = 4x + 1
y = -4x + 1
y = ¼x – 3
y = x – 1
2 and 3 since one slope is negative,
the other is positive
and they are reciprocals of each other.

9. WRAP UP (5, 19) and (-3, -1) (7, -16) and (-2, -1) (1, -4) and (0, 0)
Find the slope and perpendicular slopes
between the following sets of points.
(5, 19) and (-3, -1)
(7, -16) and (-2, -1)
(1, -4) and (0, 0)
(-6, 4) and (5, 20)
Answers:
The parallel slopes are the same.
The perpendicular slopes are….
Negative Reciprocals!
Opposite sign and flip!!!

10. Homework: Slope review worksheet
Summary:
EXPLAIN WHAT IS THE SLOPE OF A LINE: FORMULA, HORIZONTAL LINE, VERTICAL LINE
EXPLAIN HOW TO FIND THE SLOPE OF ANOTHER LINE THAT IS PARALLEL TO AN EXISTING LINE.
EXPLAIN HOW TO FIND THE SLOPE OF ANOTHER LINE THAT IS PERPENDICULAR TO AN EXISTING LINE.
Homework: Slope review worksheet