1. Equations With Variables on Both Sides
Ms. Turk, Algebra I
Unit 2-4

2. Check Skills You’ll Need
6x - 2x =
2x - 6x =
5x - 5x =
-5x + 5x =
4x + 3 = -5 4x
-4x
x = -2

3. Example A: 6x + 3 = 8x - 21 x = 12 6x + 3 = 8x - 21 - 6x - 6x
24 = 2x
x = 12
6x + 3
8x - 21

4. Example B: -6d = d + 21
-6d = d + 21
- d - d
-7d = 21
d = -3

5. Example C: m - 8 = 3m
m - 8 = 3m
- m m
-8 = 2m
-4 = m

6. This equation is called an identity.
Example D: a = 2(5 - 4a)
10 - 8a = 2(5 - 4a)
10 - 8a = a
+ 8a a
10 = 10
Always true!
This equation is called an identity.

7. This equation is an identity.
Example E: 2(x - 4) = 2x - 8
2(x - 4) = 2x - 8
2x - 8 = 2x - 8
- 2x x
-8 = -8
Always true!
This equation is an identity.

8. Identity
An equation that is true for every value of the variable. The equation 3x = 3x is an identity.