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.

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

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

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

(1.) Slope-Intercept Form**

Definition: An equation in the form of

y = mx + b

m = slope

b = y –intercept

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

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

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

Standard Form to Slope Intercept Form

How do you graph: 3x + 2y = 4?

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.

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.

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

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)