Math 121

Section 1.3

Lines in a plane and slope

Slope

Examples

1) Find the slope between the given points

a) (2,3) and (4,6)

Graph

b) (1,1) and (3,0)

c) (3,4) and (5,4)

d) (3,5) and (3,8)

Slope-intercept form of an equation

Example: Find the slope and y-intercept

Page 33

26)

28)

32)

This equation can not be expressed in slope-intercept form, so this line has no slope (undefined slope) and no y intercept

See graph below

34)

Point slope formula:

36) Write and equation of the line that passes through the given points. (Use the equation to graph the line.)

(-3,-4) and (1,4)

Find the slope first:

Next, use the point slope formula and write answer is slope-intercept form with the either point (-3,-4) and (1,4). This example use the point (1,4)

40) Write and equation of the line that passes through the given points. (Use the equation to graph the line.)

(6,1) and (10,1)

Find the slope first:

Use point-slope formula

42) Write and equation of the line that passes through the given points. (Use the equation to graph the line.

(2,5) and (2-10)

Find the slope first:

Parallel and Perpendicular Lines

Parallel lines have the same slope.

Perpendicular lines have slope that are negative reciprocals of each other.

64)

Find the slope the line.

Slope of parallel line is the same as the line

Slope of the perpendicular line would be

Find the equations

See graph