Writing Equations of Lines

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Writing Equations of Lines
CG-L6 Objectives To determine the slope
y-intercept form of a line given various inputs.
Learning Outcome B-4
2
Plot the following equations in Winplot, on the
same screen. These equations are all in
the form y mx. What is m?
Theory Deriving the Equation of a Line
3
Plot the following equations in Winplot, on the
same screen. These equations are all in
the form y mx b (where m is 1). What is b?
Theory Deriving the Equation of a Line
4
Predict the line for each equation shown. State
slope y-intercept for each case.
Example 1 Two Points
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The Slope, Y-Intercept Form of the Line
describes a straight line with slope of m and
y-intercept b. A Line is just a collection of
points. The coordinates (x,y) of each point on
the line will work in the equation (makethe
equation true). Find three points oneach line
shown
Example 1 Two Points
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Determine if the point is on the line.
(-1,1)
(0,-2)
(50,-49)
Example 1 Two Points
7
The equations of horizontal and vertical lines
look a little different. We can understand their
equations by considering each to be collections
of points, at a common distance from an
axis. Horizontal Lines Vertical Lines
Example 2 Two Points (Special Case)
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Write the equation for each line.
Example 3 Two Points (Special Case)
9
Write the equation for each line.
Example 3 Two Points (Special Case)
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Write equations in the form y mx b for the
followingstraight lines. passes
through slope y-intercept equation 4 1 -1/6 -3
(1,3) 2 (0,3) -1/2 (-3,-2) (0,1) (4,3) -1
(-1,0) 0 (5,6) undefined
Example 4 Given Slope, One Point
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Write equations in the form y mx b for the
followingstraight lines. (Hint use the slope
formula to find m, then substitute either point
to find b) passes through and (-1,-2) (1,2) (-
4,-4) (2,-1)
Example 4 Given Slope, One Point