Fri, 12/15/10

1. Fri, 12/15/10 WARM-UP: TO BE COLLECTED!1.) Find the slope of the following points (2a, 3b) and (5a, 6b) 2.) Dave graphs the functions y = x – 3 and y = 4x + 1 on the same State two ways the graphs are different. set of coordinate axes. Explain the reason for each difference. HW: CATCH UP! REVIEW PAST NOTES, HW, TESTS, QUIZZES, ETC! ~50% of the class is between grades (88%-92%, 78-82%, etc)

2. Families of linear graphs • http://www.glencoe.com/sites/texas/student/mathematics/assets/animation/algebra1/ALG1CIM4-3.swf

3. SWBAT… Write equations in slope-intercept form Mon, 1/3 Agenda • WU (10 min) • 3 practice problems to refresh our memories! (10 min) • Notes on writing equations of lines (2 examples) (20 min) • Start on hw (5 min) WARM-UP: 1. Find the slope of (2a,3b) and (5a,6b) 2. Find the slope of Ax + By = C 3. Solve for y: 5x + 4y = 80 HW#5: Writing Eqns of lines in Slope-Intercept Form

4. 1/3 What is the slope of 5x + 4y = 80 • A. m = -5 x 4 • B. m = -5 • C. m = -4 • D. m = 5 4

5. 2/3 Which equation(s) has the same y-intercept as y = ½x + 2? • A. y = 2x + 4 • B. 2 – y = ½x • C. y – 2 = x • D. y = -2 + 5x

6. 3/3 Which equation is parallel to the line -2x + 4y = 3? • A. y = -1/2 x + 5 • B. y = 2x – 6 • C. y = -2x + 4 • D. y = ½x – 2

9. 1. Set-up Cornell notes. Topic is “writing equations of lines in slope-intercept form” 2. Example 1: Write the equation of the line, in slope-intercept form, that passes through (3, 5) and (5, 9) 3. Plot (3, 5) and (5, 9) on a graph paper square and paste in your note book

10. y = mx + b • y = mx+ b is an equation that defines a line • A line has two characteristics: 1.) Slope 2.) Points that fall on the line • To write the equation of a line, you need: 1.) The slope of the line 2.) ANY point on the line

11. Ex1: Write the equation of the line, in slope-intercept form, that passes through (3, 5) and (5, 9) m = (y2-y1)/(x2-x1) Step 1: Find the slope m = (9-5)/(5-3) = 4/2 = 2 (3, 5) (5, 9) y = mx + b y = mx+b 5 = 2(3) + b OR 9 = 2(5) + b 5 = 6 + b 9 = 10 + b -1 = b -1 = b Step 2: Plug in either coordinate into y = mx + b and solve for b Step 3: Write the equation of the line by substituting the values you computed for m (step 1) and b (step 2) in y = mx + b y = mx + b y = 2x – 1 Besides (3, 5) and (5, 9), what’s another point on this line? Hint: b=-1 (0, -1)

12. Ex2: Write the equation of the line, in slope-intercept form, with a slope of 10 that passes through (-1, -4) m = 10 Step 1: Find the slope (-1, -4) y = mx + b -4 = 10(-1) + b -4 = -10 + b -6 = b Step 2: Plug in either coordinate into y = mx + b and solve for b Step 3: Write the equation of the line by substituting the values you computed for m (step 1) and b (step 2) in y = mx + b y = mx + b y = 10x – 6 Besides (-1, 4) what’s another point on this line? (0, -6)

13. Warm-Up (15 min)Tues, 1/4 Write in slope-intercept form: 1.) 2x – 3y = 12 2.) x = 2 + 3y Write the slope-intercept form of an equation of the line that satisfies each condition: 3.) Has slope 3 and y-intercept -5 4.) Passes through (5, -7) and has a slope of 3 5.) Passes through (6, -3) and (12, -3) 6.) Has an x-intercept of -2 and a y-intercept of 4 (Hint: write the two points)

14. Monday, 1/3/11: Homework: 1. Consider the points (3, 7), (-6, 1) and (9, p) on the same line. Find the value of p. 2. The x-intercept of a line is p, and the y-intercept is q. Write an equation of the line in slope-intercept form.