1. 5-Minute Check Solve each equation. Check your solution. x/3 = -6 -18

2. Objective: Solve problems using formulas.

3. To Solve an Equation means...
To isolate the variable it must be by it’s lonesome. (Have a coefficient of positive 1)
Ex: x = 5 is solved for x.
y = 2x - 1 is solved for y.

4. Example
Suppose a car travels at 55 mi/h for 3 h. How far did it travel?
d = rt
d = 55 • 3
d = 165 mi
Distance

5. Formula
shows the relationship between 2 or more quantities.
d = 2r
Diameter = 2 x radius
d = rt
distance = rate • time

6. Example
Use the formula d = 2r to find the radius of a circle that has a diameter of 18 meters.
d = 2r Diameter formula.
18 = 2r Substitute 18 for d.
18/2 = 2r/2 Divide each side by 2.
A circle with a diameter of 18 meters has a radius of 9 meters.
9 = r

7. Two – Step Equations
To isolate the variable it must be by it’s lonesome. (Have a coefficient of +1)

8. Solving Multi-Step Equations
Ex: x + 9 = 6 5

9. The DO-UNDO chart
Use a chart as a shortcut to answering the questions.
DO UNDO ÷ *5
Follow the steps in the ‘undo’ column to isolate the variable.
Ex: x + 9 = 6 5
First subtract 9.
x = 6 - 9
x = -3
Then multiply by 5.
(5) x = -3(5)
x = -15

10. Transforming Equations Containing Only Variables
Solve ab – d = c for b.
ab – d = c
+ d +d
ab = c + d
a a
DO UNDO
* a
+ d
- d
/ a

11. Solve the formula for the area of a triangle for height h.
A = ½ h B
2 * *2
B b
DO UNDO
A = ½ h B
* 1/2
/ b
* b
/ ½ (*2)

12. Homework Pg even For use do and undo charts  Look in textbook to find formulas for areas of figures