Graphing Lines

Slope – Intercept Form

Graph y = 2x + 3

Graph y = -1/3x - 2

Graph y = 3

Graph x = 4

Point Slope Form

Graph y – 2 = 2(x-1)

Graph y + 2 = ½(x+2)

Write an equation going through (4,1) with a slope of 3. Then graph it.

Write an equation going through (-2,3) with a slope of 1/2. Then graph it.

Write an equation going through (-1,-2) and (1,0). Then graph it.

Write an equation going through (5,3) and (1,1). Then graph it.

Parallel and Perpendicular Lines

• If two lines are parallel they have the same slope. This is because they are going in the same direction.

• If two lines are perpendicular, their slopes are opposite reciprocals of each other.

Examples of opposite reciprocals

What is the opposite reciprocal of each of the following?1. ½2. -33. ¾4. -5/25. 10

Are the lines parallel? Explain using the slopes

Are the following equations parallel perpendicular, or neither?1. y = 2x + 1 and y = -1/2x + 3

2. 4x+y = 2 and 2y = -8x + 10

Are the following equations parallel perpendicular, or neither?3. y = 4 – 2x and y – 2x = 10

4. x + 3y = 12 and 3x + 10 = y

Find the equation of a line parallel to y = 2x+1 that goes through (3,1)

Find the equation of a line perpendicular to y = 2x+1 that goes through (3,1)

Homework

• Pg 155 (11-27 odd)• Pg 161 (1,3, 7-19 odd)