Lesson 3-5: Slope

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Lesson 3-5 Slope

• Objectives
• Students will
• Find the slope of a line from 2 points
• Find the slope of horizontal and vertical lines
• Write equations for lines

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Slope Steepness from one point to another Ratio
of vertical change, ?y, to horizontal change,
?x. Written as
Find the slope Example 1 (3, 5) and (-2,
8) Example 2 (-5, 4) and (-1, -9)
Can consider rise or run negative but not both!!!
Doesnt matter which points is called y2 or y1 as
long as ordered pairs stay together
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Review Slopes of horizontal and vertical
lines Simply evaluate the ratio Horizontal
lines Vertical lines
H-Z- y
V-N- X
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• To write an equation with a given slope passing
  through a given point (x,y)
• Rearrange the formula for slope as follows

Get rid of fraction
Called point-slope form
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Example 3 Write an equation with a slope of
through point (-4,-10)
Start w/point slope formula
Substitute from problem
Distribute simplify
Solve for y (slope-intercept)
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• Another Method
• Writing Equations using slope ? y mx b
• Steps
• Plug in slope and given point
• Solve for b
• Write equation filling in numbers for m and b

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Example 4 Find b method Write an equation for
the line through (3, 5) with slope 2

• y mx b
• 52(3) b
• 5 6 b
• -1 b
• y 2x - 1

Start with slope-intercept
Substitute from problem
Simplify and solve for b
Put m and b into slope-intercept form
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Which method did you prefer?Why???