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Fri, 12/15/10

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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)

- http://www.glencoe.com/sites/texas/student/mathematics/assets/animation/algebra1/ALG1CIM4-3.swf

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

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

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

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

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

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

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)

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)

Write in slope-intercept form:

1.)2x – 3y = 122.) 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)

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.