Download Writing Equations in Slope

Writing Equations in
Slope-Intercept form
5.2
Three Easy Steps
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Step 1: Identify Slope
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Step 2: Identify the y-intercept
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Use slope formula if you know two points
Plug the slope and one point into the equation y =
mx + b, then solve for b
Step 3: Write the equation

Y = mx + b, insert m and b
Given Slope and Point
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Write an equation of the line that passes
through the point (6,3) and has a slope of 2.
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
Step 1
Step 2
Y = 2x +b
3 = 2(6) + b
-12 -12
-9 = b
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Step 3
Y = 2x - 9
Try it out

Write an equation of the line that passes
through the point (6,3) and has a slope
of -2.
Y = -2x + 15
Given Two Points

Write an equation of the line that passes through the
points (1,-2) and (-5,4).
M = y2 – y1 = 4 – (-2) = -1
x2 – x1
-5 – (1)
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Step 1
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Step 2
4 = -(-5) + b
-5 -5
-1 = b
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Step 3
Y = -x - 1
Y = -x + b
Try it out

Write an equation of the line that passes
through (3,0) and (2, -4)
Not the y-intercept…
what is it?
Y = 4x - 12
Real-World Problem
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
A carnival charges $2.50 per ride after
an entrance fee. You paid a total of
$22.50 after 6 rides. Write an equation
that gives the total cost as a function of
the number of rides.
What do we know?
M = 2.5
and
(6, 22.5)
Continued

Step 1
Y = 2.5x + b

Step 2
22.5 = 2.5(6) + b
-15
-15
7.5 = b
What does this tell us?

Step 3
Y = 2.5x + 7.5