1. SOLVING ONE-STEP EQUATIONS
DAY ONE
Ms. Turk, Algebra I
Unit 2-1

2. New Vocabulary
Solution: the value of the variable that makes the equation true
Equivalent Equations: equations that have the same solution
Inverse Operations: operations that undo one another, like addition and subtraction

3. Solving Equations Using Addition and Subtraction
Think of the equation like a scale. An equation is like a scale because it shows that two quantities are equal. The scale remains balanced when the same weight is added to both sides.
Let’s try some examples! Write down all the steps!

4. Example 1: Addition Solve x - 3 = 8. x - 3 + 3 = 8 + 3 x = 11
Add 3 to each side to get the variable alone on one side of the equal sign.
Simplify.

5. Example 2: Addition Solve -10 + x = -4. -10 + x = -4 + 10 + 10 x = 6
x = 6
Add 10 to each side to isolate the variable on one side of the equal sign.
Simplify.

6. Example 3: Addition Solve x - 2.5 = 6.4. x - 2.5 = 6.4 x = 8.9
Try this one on your own!
Solve x = 6.4.
x = 6.4
x = 8.9
Did you add 2.5 to both sides?
Then did you simplify?

7. Example 4: Subtraction Solve x + 8 = -2. x + 8 - 8 = -2 - 8 x = -10
Perform the inverse operation to get x by itself on one side of the equal sign.
Simplify.

8. Example 5: Subtraction Solve 3 + x = -1. 3 + x = -1 -3 -3 x = -4
x = -4
Subtract 3 from both sides to get the variable alone on one side of the equal sign.
Simplify.

9. Example 6: Subtraction Solve x + 3.4 = 7.7.
Try this one on your own!
Solve x = 7.7.
Did you subtract 3.4 from both sides?
Then did you simplify?
x = 7.7
x = 4.3

10. Real World Problem Solving
How much does the backpack weigh?
A student puts on his backpack and steps on the scale, which then reads 156 pounds. He steps on the scale alone and it reads 134 pounds. Write and solve an equation to find the weight of the backpack.
Let’s work it out!
Think Think Think!

11. Real World Problem Solving
Relate:
Define:
Write:
Backpack’s weight plus students weight equals scale reading.
Let w = backpack’s weight.
w = 156

12. Real World Problem Solving
w = 22
The backpack weighs 22 pounds.

13. Now you try! Bank Account Balance
Kate withdrew $25 from her savings account. The transaction slip said that her balance was then $ Write and solve an algebraic equation to find Kate’s previous balance.

14. Now you try! Relate: Define: Write:
Previous balance minus withdrawal equals current balance.
Let p = previous balance.
p = $347.88

15. Kate’s previous balance was $372.88.
Now you try!
p = $347.88
p = $372.88
Kate’s previous balance was $

16. Real World Problem Solving
This triangle is isosceles so sides AB and BC are congruent.
Find the value of a.
AB = BC
16 = a - 3.9
19.9 = a B 16
a - 3.9 C A

17. This triangle is isosceles so sides XY and YZ are congruent.
Now you try!
This triangle is isosceles so sides XY and YZ are congruent.
Find the value of b.
XY = YZ
b = 24
b = 61 Y
b - 37 24 X Z

18. Practice Problems
Please take a few minutes to complete the following practice problems in your notes.
n - 2 = -5
c - 4 = 9
28.32 = p
-31 = 26 + a
x = 3.75
v - 17 = 23
(-3)
(13)
(61.28)
(-57)
(-1.50)
(40)