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What Do Parallel Lines Have in Common? Lets Look at two parallel lines… Notice anything? Both Lines have different y-intercepts, but they have the SAME SLOPE… 𝒚= 𝟏 𝟑 𝒙+𝟔 𝒚= 𝟏 𝟑 𝒙−𝟏
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Write Equations of Parallel and Perpendicular Lines
Goals:• Writing Equations of Parallel Lines
• Writing Equations of Perpendicular Lines
What Do Parallel Lines Have in Common?
• Lets Look at two parallel lines…
• Notice anything?• Both Lines have
different y-intercepts, but they have the SAME SLOPE…
𝒚=𝟏𝟑 𝒙+𝟔
𝒚=𝟏𝟑 𝒙−𝟏
So for Parallel Lines…
• Two Lines are Parallel if they have the exact same slope.
• Slopes of Horizontal lines would both be Zero.
• Slopes of Vertical Lines would both be undefined.
Perpendicular Lines
• Remember: Perpendicular lines are two lines that intersect at Right Angles.
• Lets Look at a pair of Perpendicular Lines.
• Do they have anything in common?
• Slopes are different and y-intercepts can be also…
Compare:
Notice the Slopes are negative Reciprocals of each other.
Flip Fraction and change the signs for Perpendicular Slopes!
Write the Equation of a perpendicular line passing through a point
• Find the Slope of the Original Line
• Find the Perpendicular Slope.
• Use the Perpendicular Slope and the Coordinate to find the y-intercept.
• Write the equation of the line with the Perpendicular Slope and y-intercept.
