October 18th, 2007

Graph the following equations onto one sheet of graphing paper:
y = 2x + 1
y = 2x + 7
y = 2x - 3
y = 2x - 7

This is what it should look like:
(click to view it much better)


Note that..

• all these lines are parallel
• lines that are parallel have equal slopes

Parallel lines

• never touch each other
• remains the same distance away to infinity
• equal lines

Perpendicular lines

• cross forming a 90° angle
• the slopes of the two lines will be negative reciprocals

If the slope of the perpendicular is a result of a negative reciprocal then it should look like this :
m = 2/1
m"perpendicular" = -1/2


Find the equation of the line to y = 3x + 4 that goes through (7, 16).

m = 3/1
point: (7, 16)

y - y1 = m(x - x1)
y - 16 = 3/1(x - 21)
1[y - 16 = 3/1(x-21)]
y - 16 = 3x -21
y = 3x - 5

Standard Form : 0 = 3x - y - 5

Easy right? Time to use m "perpendicular":


Find the equation for the line "perpendicular" to y = 3x + 4 that goes through (7, 16)

m = 3/1
m "perpendicular" = -1/3

y - y1 = m (x - x1)
y - 16 = -1/3 (x - 7)
3[ y - 16 = -1/3 (x -7) ]
3y - 48 = x + 7

Standard Form: 0 = x + y -55


Homework: Exercise 16: Determining Equations of Lines - 3
Questions 1- 15

Test moved to Tuesday, October 23, 2007
Next scribe is KARENd, heres my other present for you c(:
Her birthday was yesterday everyone, for anyone who didnt know! :P


Cheers,
Jenn (: