1. Lesson 3.1: Solving Equations using Addition or Subtraction
Inverse Operations: math operations that undo each other
Examples: 1) Addition and Subtraction
2) Multiplication and Division
Goal when solving Equations:
- Get the variable by itself on one side of the equation

2. Addition Property of Equality: Adding the SAME number to BOTH SIDES of an equation results in an equivalent equation –Equation is still true
Subtraction Property of Equality: Subtracting the SAME number from BOTH SIDES of an equation results in an equivalent equation – Equation is still true
***Can do anything you want to an equation, as long as you do the SAME to BOTH SIDES.
Golden Rule of Algebra: Do unto one side as you do unto the other.
B.S. of Algebra : Both Sides

3. To solve an equation:
1) Simplify each side of equation
Use inverse operation
- Ask yourself “What is being done to the variable?”
- You do the INVERSE Operation to BOTH SIDES of the equation
Example: Solve. SHOW ALL WORK STEPS
1) x - 2 = -14
1) x - 2 = -14
x – =
x + (-2) + 2 =
x = -12 OR
x + (-2) = -14
x + (-2) – (-2) = -14 – (-2)
x + (-2) + 2 =
x = -12

4. x + (-11) = 8
x + (-11) – (-11) = 8 – (-11)
x + (-11) + 11 =
x = 19
Ck. x + (-11) = 8
19 + (-11) = 8
8 = 8
| -10 | + y = -21
10 + y = -21
y + 10 = -21
y + 10 – 10 = -21 – 10
y (-10) = (-10)
y = -31
Ck. | -10 | + y = -21
| -10 | + (-31) = -21
10 + (-31) = -21
-21 = -21

5. -x – 7 = 9
-x – = 9 + 7
-x + (-7) + 7 = 9 + 7
-x = 16
x = -16
6 – t = -7
6 + (-t) = -7
-t + 6 = -7
-t + 6 – 6 = -7 – 6
-t (-6) = -7 + (-6)
-t = -13
t = 13

6. -x – (-11) = -19
-x – (-11) + (-11) = (-11)
-x (-11) = (-11)
-x = -30
x = 30

7. Recall: Word problems:
1) Write knows and Finds
2) Write Verbal Model
3) Write Let statement
4) Write Equation
5) Solve using inverse operations

8. Homework: p. 135-136, #22-40 evens, #42-44 all, #46-52 evens