# SWBAT… Write and graph lines in slope-intercept form Mon, 11/14 Agenda 1.WU (10 min) 2.Video on graphing (5 min) 3.Graphing lines (10 min) 4.Writing equations.

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SWBAT… Write and graph lines in slope-intercept form Mon, 11/14 Agenda 1.WU (10 min) 2.Video on graphing (5 min) 3.Graphing lines (10 min) 4.Writing equations of lines in slope-intercept form Warm-Up: Solve each equation for y: 1. 2y = 4x + 2 2. -3y = -9x – 12 3. 21x – 7y =14 4. 2y + 26 = -6x HW5: Writing and graphing equations in slope- intercept form

When an equation is in slope-intercept form: What is the slope? ____________ Now look at the equation below…… What is the y-intercept? ____________

Converting linear equations into Slope- Intercept Form 4 Warm-UP Examples

Slope intercept form is: y = mx + b Our main goal is to get the y alone on one side of the equation

Example 1 - convert into Slope-Intercept Form (divide both sides by 2 to get y alone) (now simplify all fractions) 21 What is the slope? _____What is the y-intercept? ______

Example 2 – Convert to Slope-Intercept Form -3y = -9x – 12 Step 1: divide both sides by -3 to get y alone Step 2: Simplify all fractions Step 3: Write your equation in y = mx + b What is the slope? ____________ What is the y-intercept? ____________

*** Check Your Answer *** -3y = -9x – 12 (divide both sides by -3 to get y alone) (now simplify all fractions) y = 3x + 4 -3 -3y = -9x – 12 -3 -3 -3 Slope = 3 Intercept = 4 Wow, you’re good at this!!

Example 3: Convert to Slope-Intercept Form 21x – 7y =14 (subtract both sides by 21x) -7y = -21x + 14 (now divide both sides by -7) y = 3x – 2 (simplify all fractions) What is the slope? _________ What is the y-intercept? ________

2y + 26 = -6x Step 1: Subtract both sides by 26 Step 2: Divide both sides by 2 to get y by itself Step 3: Simplify all fractions Example 4: Convert to Slope-Intercept Form What is the slope? ____________ What is the y-intercept? ____________

2y + 26 = -6x (subtract both sides by 26) 2y = -6x – 26 (now divide both sides by 2 y = -3x – 13 (simplify all fractions) You are a math wizard! *** Check Your Answer ***

Families of Linear Graphs http://www.glencoe.com/sites/texas/ student/mathematics/assets/animati on/algebra1/ALG1CIM4-3.swf

Step 2: Look at the y-intercept and plot where the graph crosses the y-axis. Step 3: Use the slope (rise/run) to determine the next point and plot. Slope = 2/3 = 2/3 Slope = 2/3 = 2/3 Step 4: Draw a line through both points. Be sure to extend the line and put arrows at both ends. (Use a ruler!) y = 2/3x + 2 y x Step 5: Label your line Step 1: Solve for y y = 2/3x + 2

Step 2: Look at the y-intercept and plot where the graph crosses the y-axis. Step 3: Use the slope (rise/run) to determine the next point and plot. Slope = 2 = 2/1 Slope = 2 = 2/1 Step 4: Draw a line through both points. Be sure to extend the line and put arrows at both ends. (Use a ruler!) y = 2x + 1 x y Step 5: Label your line Step 1: Solve for y

Step 2: Look at the y-intercept and plot where the graph crosses the y-axis. Step 3: Use the slope (rise/run) to determine the next point and plot. Slope = -1 = -1/1 Slope = -1 = -1/1 Step 4: Draw a line through both points. Be sure to extend the line and put arrows at both ends. (Use a ruler!) y = -x – 2 y x Step 5: Label your line Step 1: Solve for y

Write the equation of the line, in slope-intercept form, that passes through (3, 5) and (5, 9) m = (y 2 -y 1 )/(x 2 -x 1 ) Step 1: Find the slope m = (9-5)/(5-3) = 4/2 = 2 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 = 2x – 1 (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 Besides (3, 5) and (5, 9), what’s another point on this line? Hint: b=-1 (0, -1)

Ex1: Write the equation of the line, in slope-intercept form, that passes through (3, 5) and (5, 9) m = (y 2 -y 1 )/(x 2 -x 1 ) Step 1: Find the slope m = (9-5)/(5-3) = 4/2 = 2 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 = 2x – 1 (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

SWBAT… Write equations in slope-intercept form Tues, 1/4 Agenda 1.WU (15 min) 2.Review hw#5 (15 min) 3.Quiz (15 min) WARM-UP: Write the slope-intercept form of an equation of the line that satisfies each condition: 1.)Has slope 3 and y-intercept -5 2.)Passes through (5, -7) and has a slope of 3 3.) Passes through (6, -3) and (12, -3) 4.) Has an x-intercept of -2 and a y-intercept of 4 (Hint: write the two points) 2 problems

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