Lesson 1-11/1-12

Solving Equations

1-11 Solving Equations

Course 3

Remember : An equation uses an equal sign to show two

expressions are equal.

In order for both sides to be balanced both sides need to be equal.

Examples of equations include:

3 + 8 = 11 24 = 31 – 7

1-11 Solving Equations

Course 3

In this lesson you will be asked to solve equations.

When solving equations find the value of the variable that makes the equation true.

Remember: This value of the variable is called the solution, or the answer to the equation

1-11 Solving Equations

Course 3

Let’s look at some equations that deal with adding a number to the variable. What are the solutions?

1. 5 + X = 17

2. N + 34 = 54

3. A + 13 = 36How do you know the value of the variables you chose are right?

1-11 Solving Equations

Course 3

Let’s try to create a general rule that will help us solve equations that deal with addition.

1. Think of a rule we can follow for solving for x in the equation 10 + x = 23. 2. Will your rule work for x + 15 = 32? 3. How about 12 + x = 15?

1-11 Solving Equations

Course 3

How about when we subtract a number from the variable such as:

X – 3 = 16

Can we write a rule for solving for x when subtracting a number?

Does your rule work for X – 12 = 15?

1-11 Solving Equations

Course 3

What about multiplying a number by a variable. How might we solve these?

3X = 15

Can you write a rule for solving for x here?

What do you think our rule might be for solving equations that deal with division like X ÷ 5 = 10

Can we summarize are rules down to just one that will work for solving all

equations?

X + 25 = 45 X ÷ 5 = 8

4X = 44X - 25 = 12

Course 3

Inverse operations are opposites, which means they “undo” each other.

To undo addition, subtractTo undo subtraction, add

To undo multiplication, divideTo undo division, multiply

1-11 Solving Equations by Adding or Subtracting

Course 3

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