### Document

```Warm Up
1. Determine if this relation is a function.
2. Find (3) if   =
2 −2
.
−1
3. Find the x-intercept and y-intercept of the graph of
3 − 5 = 15. 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 yintercept of a line.
4
,  −   4
3
Slope-Intercept Form
Option 2: Given a graph.
y
x
Slope-Intercept Form
Option 3: Given the slope and point
on the line.
1
= ,  ℎℎ 2, 3
2
Slope-Intercept Form
Option 4: Given two points on the
line.
ℎℎ 2, 3  (−1, 2)
Write an equation of the line.
1.  ℎℎ 0, −6  −4, 10 .
2.  ℎℎ 6, −2 ℎ    − 4
Point-Slope Form
The point-slope form of the equation of a line is
− 1 = ( − 1 ),
where (1 , 1 ) 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.
= −4, ℎ  ℎℎ (6, −2)
Point-Slope Form
Option 2: Given two points on the
line.
ℎℎ 2, 3  (−1, 5)
Write an equation of the line.
1.  ℎℎ 2, 3 ℎ
2.  ℎℎ −2, −1  (3, 4).
1
2
Standardized Testing
Tests 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!
= 3 − 1 and  = 3 + 13
=
1

2
and  =
1

2
+1
Example
Write 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!
= 3 − 1 and  =
= −2 and  =
1
−
3
1

2
+ 13
+1
Example
Write 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
```