 # Writing equations of parallel and perpendicular lines.

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Writing equations of parallel and perpendicular lines

X Y Y = ½X + 6 Y = -²/₁X + 0 Y = ½X - 4 Parallel lines ALWAYS have the same slope Perpendicular lines have OPPOSITE RECIPROCAL slopes

Write the equation of the line that goes through point (2, 9) and is parallel to the line Y = 2X + 3 Y = mX + b x y m 9 = (2)(2) + b 9 = 4 + b -4 5 = b Y = 2X + 5

Write the equation of the line that goes through point (-3, -5) and is parallel to the line Y = 3X - 1 Y = mX + b x y m -5 = (3)(-3) + b -5 = -9 + b +9 4 = b Y = 3X + 4

Write the equation of the line that goes through point (4, -5) and is perpendicular to the line Y = 2X + 3 Y = mX + b x ym -5 = (-½)(4) + b -5 = -2 + b +2 -3 = b Y = -½X - 3

Determine which lines if any are parallel or perpendicular a) 2X + 6Y = -3b) Y + 8 = 3X c) -15Y + 45X = 60 -2X 6Y = -3 – 2X 66 -3 6 - 2X 6 -1 1 2 3 - X - 8 Y = 3X - 8 -45X -15Y = 60 – 45X -15 60 -15 45X -15 - Y = -⅓X - ½ -4 3 1 1 + X Y = 3X - 4 Parallel lines are… b and c Perpendicular lines are… a and b a and c

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