1. 1.6 Warm Up 1.Find the slope between the points: 1.(9,3) & (-1, -6) _______________ 2.(4, -3) & (0, -3) _______________ 3.(2, 1) & (-5, 8) ________________ 4.(-4, -5) & (-4, 9) ______________

2. 1. Find the slope of the line through (-3,2) and (4, -7). 2. Find the slope of the line that passes through (–5, 6) and (0, 8). 3. Describe a line with zero slope. Give an example. 4. Describe a line with undefined slope. Give an example. 5. Find the rate of change of calories per minute. Explain what this means (in the real world). Time (min.) 20406080 Calories1755008251150 Daily Grade Only!!!!!!!!!

4. EXAMPLE 1 Identify slope and y-intercept Identify the slope and y- intercept of the line with the given equation. y = 3x + 4 1. 3x + y = 2 2.

5. EXAMPLE 1 Identify slope and y-intercept Identify the slope and y- intercept of the line with the given equation. 3x – 3y = 12 2. GUIDED PRACTICE for Example 1

6. SOLUTION EXAMPLE 2 Graph an equation using slope-intercept form Graph the equation 2x + y = 3. STEP 1 Rewrite the equation in slope-intercept form. y – 2x + 3 =

7. EXAMPLE 2 Graph an equation using slope-intercept form 4. Graph the equation y = – 2x + 5. GUIDED PRACTICE for Examples 2 and 3

8. Parallel lines have the SAME slope!!!! Perpendicular lines have opposite reciprocal slopes!!!

9. EXAMPLE 5 Identify parallel lines GUIDED PRACTICE for Examples 4 and 5 Determine which lines are parallel: line a through (-1, 2) and (3, 4); line b through (3, 4) and ( 5, 8); line c through (-9, -2) and (-1, 2). 7. SOLUTION Line a: m = 4 – 2 3 –(1) 8 – 4 5 – 3 = 2 3+1 1 2 = Line b: m = – 4 – 2 = Line c: m = 2 – (–2) – 1 – (– 9) 2+2 –1+ 9 = 4 8 = Find the slope of each line. = 2 = 1 2 Line a and line c have the same slope, so they are parallel.

10. What value for k would make the lines parallel? 1. Line 1 (-1, -4) and (0, 2) Line 2 (1, 3) and (k, 9) 2. Line 1 (-3, 9) and (-1, 1) Line 2 (-2, 10) and (1, k) k = 2 k = -2