# 4 4 Parallel and Perpendicular Lines Algebra Mr

4. 4 Parallel and Perpendicular Lines Algebra Mr. Knighton

Parallel Lines o Two non-vertical lines are parallel if and only if their slopes are equal. n n If l 1║l 2, then m 1= m 2. If m 1= m 2, then l 1║l 2. m 1 l 1 Parallel and Perpendicular Lines m 2 l 2 2

Write the equation of the line that passes through (3, 6) and is parallel to y = 2/3 x+2. m = 2/3 and the point is (3, 6) y = mx+b 6 = 2/3(3)+b 6 = 2+b 4=b y = 2/3 x+4 Parallel and Perpendicular Lines 3

Write the equation of the line that passes through (4, -5) and is parallel to y = -2 x-4. m = -2 and the point is (4, -5) y = mx+b -5 = -2(4)+b -5 = -8+b 3=b y = -2 x+3 Parallel and Perpendicular Lines 4

Write the equation of the line that passes through (-6, 4) and is parallel to y=1/3 x-1. m=1/3 and the point is (-6, 4) y =1/3 x+6 Parallel and Perpendicular Lines 5

Perpendicular Lines o Two non-vertical lines are perpendicular if and only if the product of their slopes is -1. n n If l 1┴l 2, then m 1 ● m 2= -1. l 1 If m 1● m 2 = -1, then l 1┴l 2. Slopes are negative reciprocals Parallel and Perpendicular Lines m 1 m 2 l 2 6

Write the equation of the line that passes through (6, -5) and is perpendicular to y = 2 x+3. m = -1/2 and the point is (6, -5) y = mx+b -5 = -1/2(6)+b -5 = -3+b -2 = b y = -1/2 x-2 Parallel and Perpendicular Lines 7

Write the equation of the line that passes through (6, -7) and is perpendicular to y = 2/3 x+1. m = -3/2 and the point is (6, -7) y = mx+b -7 = -3/2(6)+b -7 = -9+b 2=b y = -3/2 x+2 Parallel and Perpendicular Lines 8

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