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The Line
• A line is created when any 3 points
or loci (locus, singular) are
aligned.
• We can describe a line with the
function format equation,
• y = ax + b
• Where a is the slope
• And b is the y intercept.
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The Line
• We can also use the equation,
• Ax + By + C = 0
• Where A nor B are zero.
• This can be reorganized into the
more familiar function format.
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Activity
• Express
• 2x + 3y – 2 = 0 in function format.
• Determine the equation of a line
that goes thru’ points (1,2) and (3,-6).
• Determine the equation of a line
that is midway and perpendicular to
the previous 2 points.
• a -1/a for perpendicular line
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Symmetric Format
• x + y = 1
a b
• where a is the x intercept and b is
the y intercept.
• E.g. x/2 + y/5 = 1
• Gives us (2,0)… x intercept
• And (0,5)…y intercept.
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Example
• Express x/2 + y/5 = 1 in function
format.
• Multiply by 10 (5x2) to get rid of
the fractions on both sides.
• This gives 5x + 2y = 10
• Isolate the 2y…2y = -5x + 10
• Isolate the y….y = -5/2 x + 10/2
• y = -2.5x + 5
