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Warm Up1. Determine if this relation is a function.
2. Find if .
3. Find the x-intercept and y-intercept of the graph of . The graph the equation.
4. Find the slope of a line that passes through (3, 5) and (4, 1).
2.4 Writing Equations of Lines
The slope intercept form of the equation of a line is where is the ___________ and is the _____________.
Slope-Intercept Form
Option 1: Given the slope and y-intercept of a line.
Slope-Intercept Form
Option 2: Given a graph.y
x
Slope-Intercept Form
Option 3: Given the slope and point on the line.
Slope-Intercept Form
Option 4: Given two points on the line.
Try It On Your Own.
Write an equation of the line.1. .
Point-Slope FormThe point-slope form of the equation of a line is
,
where are the coordinates of a point on the line and is the slope of the line.
Point-Slope Form
Option 1: Given the slope and a point on the line.
Point-Slope Form
Option 2: Given two points on the line.
Try It On Your Own
Write an equation of the line.
1. .
Standardized TestingTests like HSAP or the COMPASS love to ask questions like this…
Which is an equation of the line that passes through (-2, 7) and (3, -3)?
A.
B.
C.
D.
Parallel Lines
How do you know if two lines are parallel?
Their SLOPES are the SAME!
and
and
ExampleWrite an equation of a line that passes through (12, 0) and is parallel to .
Write an equation of a line that passes through (0, 9) and is parallel to .
Perpendicular Lines
How do you know if two lines are perpendicular?
Their SLOPES are the NEGATIVE RECIPROCALS!
and
and
ExampleWrite an equation of a line that passes through (5, -6) and is perpendicular to .
Write an equation of a line that passes through (6, -1) and is parallel to .
Summary
Slope-Intercept Form:
Point-Slope Form:
Parallel Lines:
Perpendicular Lines:
Homework!!! YAY!
Lesson 2.4 Page 87#’s 9, 13, 15, 17-19, 23, 24 and 32
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