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Drill #63
• Write a direct variation equation that relates x to y. Assume that y varies directly as x. Then solve.
1. If y = 8 when x = 2, find x when y = 26.
2. If y = 2 when x = -1, find y when x = 20.
3. If y = ½ when x = ¾ , find x when y = 6.
4. If y = -2 when x = 8, find y when x = 24.
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Drill #64Write a direct variation equation that relates x
to y. Assume that y varies directly as x. Then solve.
1. If y = ½ when x = ¼ , find x when y = 6.
2. If y = -2 when x = -6, find y when x = 9.
Graph the following direct variation equations.
3. y = -3x
4. y = ¾ x
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Drill #65A. Identify the slope (m) and the y-intercept (b)
of each equation.B. Graph each equation
1. y = 3x + 2
2. y = - ¾ x – 1
3. y = ¼ x
4. y = 2
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4-3 Graphing Equations in Slope Intercept Form
Objective: Write and graph linear equations in slope intercept form, and model real-world data with an equation in slope-intercept form
Pg. 204
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(1.) Slope-Intercept Form**
Definition: An equation in the form of
y = mx + b
m = slope
b = y –intercept
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Write an Equation Given the Slope and Y-intercept*
To write an equation of a line given the slope and the y- intercept substitute the slope (m) and the y- intercept (b) into the equation y = mx + b
Ex1:
1:
Classwork: 4-3 Study Guide #1-3
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Write an Equation From a Graph*
To write an equation given a graph:
1. Find the slope (m) of the line.
2. Identify the y-intercept (b)
3. Substitute m and b into the equation
y = mx + b
Ex2:
2:
Classwork: 4-3 Study Guide #4-6
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Graphing Equations in Slope- Intercept Form*
To graph an equation in slope-intercept form:
1. Plot the y-intercept (b) on the y- axis
2. Use the slope (m) to plot a second point
3. Connect the dots (and draw arrows)
Ex3a,b:
3.
Classwork: 4-3 Study Guide #7-9
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Standard Form to Slope Intercept Form
How do you graph: 3x + 2y = 4?
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Standard Slope Intercept*
To convert an equation from standard form to slope intercept:
1. Subtract the x term from both sides of the equation
2. Divide both side by the y coefficient
Note: This is solving the equation for y.
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Standard Slope Intercept*
Formulas:
Standard Form: Ax + By = C
Slope Intercept Form: y = mx + b
m = -A/B
b = C/B
Ex 3b.
Classwork: 3C, 3D.
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Writing Equations from Word Problems*
To write equations in slope intercept form from word problems:
1. Slope (m) is the rate (per)
2. The y-intercept (b) is the starting point (when x = 0)
Ex: 4-3 Study Guide #15
Classwork: #16-18
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Slope Intercept in Word Problems
Write equations to represent the situations from 4-3 Word Problem Practice
- You may work in groups of up to 3.
- Off topic conversations (-1 part. point)
- Selected groups will present their problems (if there is time)