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Parallel Lines = Lines in the same plane that never intersect. Review: Slope-Intercept form: y = mx+b Write an equation in slope-intercept form for both of the lines below….what do you notice? y = ⅔x + 5 y = ⅔x - 3 Parallel Lines have the SAME slope and DIFFERENT y-intercepts. To determine whether lines are parallel, you just compare the slopes and the y-intercepts… If slopes are the same and different y-intercepts If slopes are the same and the same y-intercepts – the lines are parallel - you have the same line If slopes are different – the lines are not parallel 1. y = -⅓x + 5 and 2x + 6y = 12 2. -6x + 8y = -24 and y = ¾x - 7 3x + 4y = 12 and y = ½x + 5 1. Identify the slope of the given line 2. Write an equation in Point-Slope form using the identified slope and the given point. y – y1 = m(x – x1) 3. Convert to Slope-Intercept form (solve for y) y = mx + b Write an equation in slope-intercept form for the line that contains (8, 2) and is parallel to y = ⅝x - 4 Write and equation in slope-intercept form for the line that contains (2, -6) and is parallel to y = 3x + 9 Perpendicular Lines = Lines that intersect to form right angles (90°) Write an equation in slope-intercept form for both of the lines below….what do you notice? y = -(4/3)x + 5 y = ¾x + 3 The slopes of perpendicular lines are negative reciprocals of each other. Negative reciprocals: Ex. The negative reciprocal of ½ is -2. The negative reciprocal of -¾ is 4/3. What is the slope of a line perpendicular to… y = ⅝x + 5 6x + 8y = 24 Are each pair of lines parallel, perpendicular, or neither? y = 3x – 8 and 3x – y = -1 Are each pair of lines parallel, perpendicular, or neither? 9x + 3y = 6 and 3x + 9y = 6 Are each pair of lines parallel, perpendicular, or neither? y = -(5/2)x + 11 and -5x + 2y = 20 Write an equation in slope-intercept form of the line that contains (1, 8) and is perpendicular to y = ¾x + 1.