Download 7-3 Writing equations in Slope

7-3 Writing equations in SlopeIntercept form
• Objectives: Write a linear equation in Slope-intercept
form given the slope and y intercept
Questions
• What is the format for slope intercept form?
• What do the variables “m” and “b” mean
and what do they tell you?
• What part of the graph will you find “b”,
what axis?
• What’s do you do after you have plotted “b”
• If you are given only 2 points, describe the
steps to placing the equation in slope
intercept form.
Linear Equations (y = mx + b)
• b = y-intercept
• plot (0,b) to get your first point
• m = slope
rise
• written as a fraction slope =
/run
• Lean right if positive
• Lean left if negative
7-3
• Slope intercept form:
y=mx+b
The y intercept,
Where it crosses the y
line
The y coordinate
The x coordinate
Slope rise/run
Linear Equations (y = mx + b)
b = -3 (y-intercept)
y = 1/3 x - 3
plot (0,-3)
m = 1/3 (slope rise/run)
positive leans right
plot up 1, right 3
plot down 1, left 3
connect the points
Linear Equations (y = mx + b)
b = 2 (y-intercept)
y = -1/2 x + 2
plot (0,2)
m = -1/2 (slope rise/run)
negative leans left
plot up 1, left 2
plot down 1, right 2
connect the points
7-3
Given the slope m
and the y intercept
write an equation in slope intercept form
m= -3
b= -2
Step1: write the equation
Step 2: substitute the given numbers
b
7-3
• The equation can then be graphed
y=-3x-2
b=-2
m= -3
y= -3x-2
7-3
• Sometimes you may have to manipulate the equation to get it in
slope-intercept form
4x-2y=8
Subtract the 4x from both sides
Divide all by -2 to isolate y
Given two points, write the equation of a line
in slope intercept form
GIVEN: (2,-3) and (4,-2)
Steps:
1. Find slope
2. Place a point and
the slope in into point
slope form
3. Distributive
property
4. Additive
property
of equality