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Warm Up 1. Determine if this relation is a function. 2. Find (3) if = 2 −2 . −1 3. Find the x-intercept and y-intercept of the graph of 3 − 5 = 15. The graph the equation. 4. Find the slope of a line that passes through (3, 5) and (4, 1). 2.4 Writing Equations of Lines The slope intercept form of the equation of a line is = + where is the ___________ and is the _____________. Slope-Intercept Form Option 1: Given the slope and yintercept of a line. 4 , − 4 3 Slope-Intercept Form Option 2: Given a graph. y x Slope-Intercept Form Option 3: Given the slope and point on the line. 1 = , ℎℎ 2, 3 2 Slope-Intercept Form Option 4: Given two points on the line. ℎℎ 2, 3 (−1, 2) Try It On Your Own. Write an equation of the line. 1. ℎℎ 0, −6 −4, 10 . 2. ℎℎ 6, −2 ℎ − 4 Point-Slope Form The point-slope form of the equation of a line is − 1 = ( − 1 ), where (1 , 1 ) are the coordinates of a point on the line and is the slope of the line. Point-Slope Form Option 1: Given the slope and a point on the line. = −4, ℎ ℎℎ (6, −2) Point-Slope Form Option 2: Given two points on the line. ℎℎ 2, 3 (−1, 5) Try It On Your Own Write an equation of the line. 1. ℎℎ 2, 3 ℎ 2. ℎℎ −2, −1 (3, 4). 1 2 Standardized Testing Tests like HSAP or the COMPASS love to ask questions like this… Which is an equation of the line that passes through (-2, 7) and (3, -3)? A. = − B. = − + C. = + D. = + Parallel Lines How do you know if two lines are parallel? Their SLOPES are the SAME! = 3 − 1 and = 3 + 13 = 1 2 and = 1 2 +1 Example Write an equation of a line that passes through (12, 0) and is parallel to = − − . Write an equation of a line that passes through (0, 9) and is parallel to = − . Perpendicular Lines How do you know if two lines are perpendicular? Their SLOPES are the NEGATIVE RECIPROCALS! = 3 − 1 and = = −2 and = 1 − 3 1 2 + 13 +1 Example Write an equation of a line that passes through (5, -6) and is perpendicular to = − + . Write an equation of a line that passes through (6, -1) and is parallel to = − . Summary Slope-Intercept Form: Point-Slope Form: Parallel Lines: Perpendicular Lines: Homework!!! YAY! Lesson 2.4 Page 87 #’s 9, 13, 15, 17-19, 23, 24 and 32