Algebra 1
Section 4.6
Quick Graphs Using SlopeIntercept Form
Important!!!
This is a big concept in Algebra 1.You
need to thoroughly understand this!
Slope – Intercept Form
y = mx + b
m represents the slope
b represents the y-intercept
Writing Equations
y  m x b
When asked to write an equation,
you need to know two things –
slope (m) and y-intercept (b).
Example 1: Writing Equations
Write an equation in slope-intercept form of the line
that has a slope of 2 and a y-intercept of 6.
To write an equation, you need two things:
slope (m) = 2
y – intercept (b) = 6
We have both!! Plug them into slope-intercept form
y = mx + b
y = 2x + 6
Writing Equations
Write an equation in slope-intercept form
for the following:
1.
m  1
b2
3. m  0
b  4
2.
1
m 
2
3
b 
2
4. m  0.5
b  4
Write the equation of a line that has a
y-intercept of -3 and a slope of -4.
y = -3x – 4
2. y = -4x – 3
3. y = -3x + 4
4. y = -4x + 3
1.
To find the slope and y-intercept of
an equation, write the equation in
slope-intercept form: y = mx + b.
Find the slope and y-intercept.
1) y = 3x – 7
y = mx + b
m = 3, b = -7
Find the slope and y-intercept.
2
2) y = 3 x
y = mx + b
y= 2x+0
2
m=
3
b=0
3
3) y = 5
y = mx + b
y = 0x + 5
m=0
b=5
Find the slope and y-intercept.
4) 5x - 3y = 6

5
m=
3
b = -2
Find the slope and y-intercept.
5) 2y + 2 = 4x
Write it in slope-intercept form.
(y = mx + b)
2y + 2 = 4x
-2
-2
2y = 4x – 2
2
2
2
y = 2x - 1
m=2
b = -1
Find the slope and y-intercept of
y = -2x + 4
m = 2; b = 4
2. m = 4; b = 2
3. m = -2; b = 4
4. m = 4; b = -2
1.
Example 2: Graphing Using
Slope and y-Intercept
When given an equation, you can easily
graph it in slope-intercept form. All you
need is two things–
the slope (m) and y-intercept (b).
Graphing Using Slope
and y-intercept
Step
1:
Make sure the equation
is in slope-intercept form
Step 2:
Find the slope and yintercept
Step 3:
Plot the y-intercept
Step 4:
Apply the slope
(rise/run) to the y-intercept
Review: Graphing with slope-intercept
1
y
x2
3
1.
2.
3.
4.
Start by graphing the
y-intercept (b = 2).
From the y-intercept,
apply “rise over run”
using your slope.
rise = 1, run = -3
Repeat this again from
your new point.
Draw a line through
your points.
-3
1
-3
1
Start here
Graph:
y  2x  3
Step 1:
y=mx+b
Step 2:
slope = 2 y-intercept = 3
Step 3:
plot the y-intercept on a graph
Step 4:
apply the slope
y  2x  3
Graph the following equations:
y  2x 1
y  6 x
Homework:
Complete Study Guide for
Chapter 4  due Tuesday,
November 19th