Writing Equations of Parallel and Perpendicular Lines y-y1=m(x-x1) Writing Equations of Parallel and Perpendicular Lines J. Bradford

Notes Slide Point-slope form of an equation: y-y1=m(x-x1) When writing an equation of the line, remember that you need two pieces of information: 1.) Any point on the line 2.) the slope To find the slope, you must remember two rules. Parallel lines have the same slope. Ex: If the slope is -4, the parallel slope will be -4. Perpendicular lines have negative reciprocal slopes of each other. Ex: If the given slope is 3, the perpendicular slope will be -1/3. After you get this information, plug the x and y values from your point and the slope (m) value into the formula and solve for y.

Practice Problem #1 Which of the following is an equation of the line that passes through (3,-5) and has a slope parallel to 2? y=2x-11 y=2x+11 y=3x-1 D. y=3x-11

Practice Problem #2 Which of the following is an equation of the line that passes through (2,-1) and is parallel to ? Y=- ½ x-1 Y=- ½ x+3 Y=- ½ x D. y=2x+1

Practice Problem #3 Write an equation for the line that passes through (-2,-5) and is parallel to the line y=4x-1. y=4x-22 y=4x+3 y=4x+18 D. y=4x-3

Practice Problem #4 Write an equation of the line that passes through (1,6) and is parallel to the line x+y=-4. y=x+5 y=-x+7 y=x+7 D. y=-x-7

Practice Problem #5 Find the equation of the line parallel to the line whose equation is y=-3x+5 and which passes through the point (3,-2). Y= -3x-7 y=-3x+11 y=- x-1 D. y= x+3

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