Ch 4.1 (part 2) Slope (formula) Objective: To find the slope of a line when given two points.

Distribute the negative: change the signs for x1 and y1 Definition Slope (m): formula m = y2 – y1 x2 – x1 where (x1, y1) is a point and (x2, y2) is another point. It is important to keep the coordinates “in line” otherwise the sign will be reversed. Use when given 2 points EASY way to find the slope (x2, y2) − − ( x1, y1) - - Distribute the negative: change the signs for x1 and y1 y2 – y1 x2 – x1

Example 1 Example 2 (-1, 3) (6, 5) ( 4, 7) (-1, 7) m = m = Find the slope between (-1, 3) and (4, 7). Find the slope between (6, 5) and (-1, 7). (-1, 3) (6, 5) − − − ( 4, 7) - - − (-1, 7) - − 3 - 7 5 - 7 -4 -2 = = -1 - 4 6 + 1 -5 7 4 -2 m = m = 5 7

Example 3 Example 4 (-8, 7) (1, 2) ( 4, 1) (-2,-3) m = m = Find the slope between (-8, 7) and (4, 1). Find the slope between (1, 2) and (-2,-3). (-8, 7) (1, 2) − − − ( 4, 1) - - − (-2,-3) − − 7 - 1 2 + 3 6 5 = = -8 - 4 1 + 2 -12 3 -1 5 m = m = 2 3

Example 5 Example 6 (-3, 2) (-1, 4) ( 4, 2) (-1,-5) m = m = Find the slope between (-3, 2) and (4, 2). Find the slope between (-1, 4) and (-1,-5). (-3, 2) (-1, 4) − − − ( 4, 2) - - − (-1,-5) − − 2 - 2 4 + 5 9 = = -3 - 4 -1 + 1 -7 m = m = undefined

Find the slope between the following points. Classwork Find the slope between the following points. 1) (1, 2) & (3, 4) 2) (-3, 4) & (1, 2) 3) (2, 5) & (4, 8) 4) (4, 5) & (1, 5)

5) (7, 3) & (5, 4) 6) (3, 6) & (5, 3) 7) (6, 2) & (6, 7) 8) (10, 5) & (5, 5)