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4.7 Graphing Using Slope-Intercept Form. Hopefully you remember from last section, that we can graph a line easily when given: 1. a random point 2. the slope of the line. Let’s do an example of this: Point (2,3) Slope = 2.
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Hopefully you remember from last section, that we can graph a line easily when given: 1. a random point 2. the slope of the line
Let’s do an example of this: Point (2,3) Slope = 2
Wouldn’t it be great if we could just look at an equation and figure out it’s slope and a point???!!! WE CAN!!! YAHHHH!!!! BY USING SLOPE-INTERCEPT FORM
SLOPE-INTERCEPT FORM EXAMPLE #1 So all we have to do is solve for “y” and we can see a slope and a point!!!
Some more examples… “b” is the y-intercept
Let’s practice converting an equation to slope-intercept form. In other words: SOLVE FOR “y” 2x – y = -3 2. 4x + 2y = 6 3. -5x – 3y = 15 4. 4x + 3y = 24 -2x -2x -y = -2x – 3 y = 2x + 3 -4x -4x 2y = -4x + 6 y = -2x + 3 -4x -4x 3y = -4x + 24 +5x +5x -3y = 5x + 15
Now let’s look at each equation and decide what the slope and y-intercept is. y = mx + b y = -3x + 6 2. y = 2x – 5 3. y = -x 4. 2y = 8x +10 5. x + 3y = 9 6. x – 2y = 16 m = b = (0,6) m = b = (0,-5) y = 4x + 5 m = b = (0,0) m = b = (0,5) m = b = (0,3) m = b = (0,-8)
Now we can finally graph using slope-intercept form. y = mx + b y = -3x + 2 m = b = (0,2)
Graph using slope-intercept form. y = mx + b x + y = 0 y = -x m = b = (0,0)
Graph using slope-intercept form. 3x - 3y = 9 -3x -3x -3y = -3x + 9 -3 -3 -3 y = x - 3 m = b = (0,-3)
Graph using slope-intercept form. 4x + 5y = 15 -4x -4x 5y = -4x + 15 5 5 5 m = b = (0,3)
Graph using slope-intercept form. 4x - y – 3 = 0 -4x -4x - y – 3 = -4x +3 +3 -y = -4x + 3 m = b = (0,-3)
Graph using slope-intercept form. 2x - 3y – 6 = 0 -2x -2x -3y – 6 = -2x +6 +6 -3y = -2x + 6 -3 -3 -3 m = b = (0,-2)
Graph using slope-intercept form. x – y + 4 = 0 -x -x -y + 4 = -x -4 -4 -y= -x - 4 -1 -1 -1 m = b = (0,4)
Graph using slope-intercept form. m = b = (0,1)
Now I want you to graph these two equations on the same graph THESE LINES ARE PARALLEL!! THEY HAVE THE SAME SLOPE y = mx + b m = b = (0,3) m = b = (0,-2)
Are these lines parallel??? a.) -x + 2y = 6 b.) -x + 2y = -2 c.) x + 2y = 4 +x +x +x +x 2y = x + 6 2y = x - 2 y = mx + b 2 2 2 2 2 2 -x -x “a” and “b” are parallel 2y = -x + 4 2 2 2
For each problem, tell me if the two equations are parallel. y = mx + b 1. y = -3x + 2 y + 3x = -4 2. 2x – 12 = y y = 10 + 2x 3. y = x + 8 x – y = -1 4. 2x – 5y = -3 5x + 2y = 6 y = -3x - 4 Yes!!!!! y = 2x - 12 Yes!!!!! y = 2x + 10 Yes!!!!! y = x + 1 No!!!!
Write the equation of a line that has a y-intercept of -3 and a slope of -4. • y = -3x – 4 • y = -4x – 3 • y = -3x + 4 • y = -4x + 3
Write an equation of the line that goes through the points (0, 1) and (1, 4). • y = 3x + 4 • y = 3x + 1 • y = -3x + 4 • y = -3x + 1
Find the slope and y-intercept.4) 5x - 3y = 6 Write it in slope-intercept form. (y = mx + b) 5x – 3y = 6 -3y = -5x + 6 y = x - 2 -3 -3 -3 m = b = -2
Find the slope and y-intercept. 5) 2y + 2 = 4x Write it in slope-intercept form. (y = mx + b) 2y + 2 = 4x 2y = 4x - 2 y = 2x - 1 2 2 2 m = 2 b = -1
Find the slope and y-intercept of y = -2x + 4 • m = 2; b = 4 • m = 4; b = 2 • m = -2; b = 4 • m = 4; b = -2