1. Parallel and Perpendicular Lines
Pre AP Geometry
Please use this presentation to complete the notes for a DIY grade
Thank you 

2. Parallel Lines
Parallel lines remain the same distance apart over their entire length.
To show that lines are parallel we draw small arrow marks on them.
Shorthand: If you want to talk about two parallel lines there is a shorthand that can be used. For example, if you want to say that line PQ is parallel to line RS you could write :
PQǁRS
When looking at two equations parallel lines will have the SAME SLOPE.

3. So looking at the equations which lines would be parallel to each other?
A) y=2x+1
y =3x+1
B) y=1/2x+5
y=1x+1
C) y=3x+1
y=3x+5

4. If you guessed C you are right!
Remember: when you are looking at the form of y=mx+b…
y=mx+b
For C the slopes are the same:
C) y=3x + 1
y=3x + 5
Y-Intercept
Slope

5. Perpendicular Lines C A B D
Perpendicular lines are two lines that meet at a right angle.
To write that line AB is perpendicular to line CD.
AB CD
When looking at two equations perpendicular lines have opposite and reciprocal slopes. C A B D

6. Looking at the equations which pair of lines are perpendicular?
A) y=2/3x+1
y= 3x +2
B) y= 4x+2
y= 4x+5
C) y=2x+1
y=2x+1
D) y= 1/2X+2
y =-2X+2

7. D is Correct! Remember we are interested in the slopes
Y=1/2x + 2
Y=-2x + 2
So since ½ is positive we want a negative
Now if you flip ½ over you will get 2/1 which is the same thing as 2.
So we get -2

8. Skew Lines Non-Coplanar lines that do not Intersect.
Not on the same plane