Do you know how to evaluate a variable expression when it includes powers? Take a look at this problem.

for

Evaluating dilemmas like this one is just what this Concept is all about. Pay attention and you will be able to work through this problem at the end of the Concept.

### Guidance

Did you know that you can apply the order of operations to expressions that have powers in them?

Let's look at how to do this.

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To do this, we are going to need to refer back to the order of operations.
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Order of Operations
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P parentheses or grouping symbols
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E exponents
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MD multiplication and division in order from left to right
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AS addition and subtraction in order from left to right
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Now look at the E. That E refers to exponents and powers and evaluating exponents in the order of operations. You can see that you evaluate the powers right after the grouping symbols.
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It is a bit like working on a puzzle. Here is an expression that needs evaluating.

Evaluate the expression . Let .

It does look complicated, but if it helps, think of this as a series of steps. The order of operations is your guide. If you follow the order of operations then working through a problem such as this one becomes much easier.

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The answer is 126.
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We can also evaluate variable expressions that have more than one variable. Notice that a different value has been given for
and
. You simply substitute the given values into each expression and evaluate it for the quantity of the expression.
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Evaluate the expression . Let and .

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The answer is 117.
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When you have variable and numerical expressions with powers in them, you can use the order of operations to evaluate the expressions. Remember not to get stuck if the problem seems complicated. Stick to the order of operations and you will be able to evaluate the expression.
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#### Example A

Evaluate the expression for .

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Solution:
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#### Example B

Evaluate the expression for .

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Solution:
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#### Example C

Evaluate the expression for .

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Solution:
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Now let's go back to the dilemma from the beginning of the Concept. Evaluate this expression.

for

First, let's substitute the given values into the expression for and .

for

Now we can evaluate the powers. Here is our answer so far.

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This is our final answer.
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### Vocabulary

- Numerical Expression
- A numerical expression is a group of numbers and operations used to represent a quantity.

- Variable Expression
- A variable expression is a mathematical phrase that contains at least one variable or unknown quantity.

- Power
- The "power" refers to the value of the exponent. For example, is "three to the fourth power".

- Base
- When a value is raised to a power, the value is referred to as the base, and the power is called the exponent. In the expression , 32 is the base, and 4 is the exponent.

- Exponent
- Exponents are used to describe the number of times that a term is multiplied by itself.

### Guided Practice

Here is one for you to try on your own.

Evaluate the expression for .

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Solution
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Step 1:
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Before performing the order of operations, substitute 6 for “
.”

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Step 2:
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Perform the calculations inside the parentheses.

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Step 3:
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Perform the calculations with exponents.

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Step 4:
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Multiply

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Step 5:
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Add

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The answer is -1,464.
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### Video Review

Khan Academy Introduction to the Order of Operations

### Explore More

Directions: Evaluate each expression. Remember to follow the order of operations.

Directions: Evaluate each expression by substituting the given value into each expression. Remember to follow the order of operations.

6. for .

7. for .

8. for .

9. for .

10. for .

11. for .

12. for .

13. for .

14. for .

15. for .

16. for .