# A3 2.4 Parallel and Perpendicular Lines, Avg. rate of change

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A3 2.4 Parallel and Perpendicular Lines, Avg. rate of change
Homework: p 1-29 odd

Slope and Parallel LInes
If 2 non-vertical lines are parallel, they have the same slope. If 2 distinct non-vertical lines have the same slope, then they are parallel. Two distinct vertical lines, both with undefined slopes, are parallel. Guided Practice: Write an equation of the line passing through (-3,1) that is parallel to y = 2x + 1.

Slope and perpendicular lines
If two non-vertical lines are perpendicular, then the product of their slopes is a – 1. (the 2 slopes are negative reciprocals of each other) If the product of the slopes of 2 lines is a -1, then the 2 lines are perpendicular. A horizontal line having a slope of zero is perpendicular to a vertical line having undefined slope. Guided Practice: Write the equation of the line passing through (3,-5) and perpendicular to x + 4y – 8 = 0. Express your answer in general form.

Average Rate of change If the graph of a function is not a straight line, the average rate of change between 2 points is the slope of the line containing the 2 points. The line is called a secant line. Average Rate of Change: Example:

Whiteboard Practice Write an equation in slope-intercept form for the line parallel to y = - 5x + 4 and passing thru (-2, -7). Write an equation in slope-intercept form for the line perpendicular to x + 7y – 12 = 0 and passing through (5, -9) The graph of f passes through (-5, 6) and is perpendicular to the line that has an x-intercept of 3 and a y-intercept of -9. Write an equation in slope intercept form.

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