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# 9.3: Simplification of Radical Expressions

Difficulty Level: At Grade Created by: CK-12
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Have you ever watched a baseball game? Have you ever seen a runner run so fast that he passed the intended base? Take a look at what Miguel saw.

Miguel was watching a game on Saturday night. During the fourth inning, the runner ran from second base to third base. He was running to fast that he ran past third base and had to come back to reach the base.

The runner ran $90 + \sqrt 16$ .

How far did the runner run?

This situation has been described using a radical expression. You will learn how to evaluate radical expressions in this Concept.

### Guidance

Sometimes, we can have an expression with a radical in it.

What is a radical?

A radical is the name of the sign that tells us that we are looking for a square root. We can call this “a radical.” Here is a radical symbol.

$\sqrt{y}$

Here we would be looking for the square root of $y$ .

What is a radical expression?

Remember than an expressions is a number sentence that contains numbers, operations and now radicals. Just as we can have expressions without radicals, we can have expressions with them too.

Let's look at one.

$2 \cdot \sqrt{4} + 7$

Here we have two times the square root of four plus seven.

That’s a great question! We can evaluate this expression by using the order of operations.

P parentheses

E exponents (square roots too)

MD multiplication/division in order from left to right

AS addition/subtraction in order from left to right

According to the order of operations, we evaluate the square root of 4 first.

$\sqrt{4} = 2$

Next, we substitute that value into the expression.

$2 \cdot 2 + 7$

Next, we complete multiplication/division in order from left to right.

$2 \times 2 = 4$

Substitute that given value.

$4 + 7 = 11$

The answer is 11.

Let’s look at another one.

$\sqrt{4} \cdot \sqrt{16} - 3$

Here we have two radicals in the expression. We can work the same way, by using the order of operations.

Evaluate the radicals first.

$\sqrt{4} & = 2\\\sqrt{16} & = 4$

Substitute these values into the expression.

$2 \cdot 4 - 3$

Next, we complete multiplication/division in order from left to right.

$2 \times 4 = 8$

Finally, we complete the addition/subtraction in order from left to right.

$8 - 3 = 5$

The answer is 5.

Evaluate each radical expression.

#### Example A

$6 + \sqrt{9} - \sqrt{49} + 5$

Solution: $7$

#### Example B

$\sqrt{64} \div \sqrt{4} + 13$

Solution: $17$

#### Example C

$6(7) + \sqrt{121} - 3$

Solution: $50$

Here is the original problem once again.

Miguel was watching a game on Saturday night. During the fourth inning, the runner ran from second base to third base. He was running to fast that he ran past third base and had to come back to reach the base.

The runner ran $90 + \sqrt 16$ .

How far did the runner run?

To figure this out, we have to evaluate the radical expression.

The distance from one base to another is 90 feet.

The extra distance is the $\sqrt 16$ . Let's evaluate that part first.

$\sqrt 16 = 4$

Now let's add that into the original expression.

$90 + 4 = 94$

The runner ran 94 feet.

### Vocabulary

Here are the vocabulary words in this Concept.

Square Number
a number of units which makes a perfect square.
Square root
a number that when multiplied by itself equals the square of the number.
Perfect Square
square roots that are whole numbers.
Radical
the symbol that lets us know that we are looking for a square root.
Radical Expression
an expression with numbers, operations and radicals in it.

### Guided Practice

Here is one for you to try on your own.

Evaluate this radical expression.

$8(7) + \sqrt{144} - 9$

Answer

First, let's evaluate the square root.

$\sqrt 144 = 12$

Now we can substitute 12 back into the original expression and solve using the order of operations.

$8(7) + 12 - 9$

$56 + 12 - 9$

$68 - 9 = 59$

Our answer is $59$ .

### Video Review

Here is a video for review.

### Practice

Directions: Evaluate each radical expression.

1. $2 + \sqrt{9} + 15-2$

2. $3 \cdot 4 + \sqrt{169}$

3. $\sqrt{16} \cdot \sqrt{25} + \sqrt{36}$

4. $\sqrt{81} \cdot 12 + 12$

5. $\sqrt{36} + \sqrt{47} - \sqrt{16}$

6. $6 + \sqrt{36} + 25-2$

7. $4(5) + \sqrt{9}-2$

8. $15 + \sqrt{16} + 5$

9. $3(2) + \sqrt{25} + 10$

10. $4(7) + \sqrt{49}-12$

11. $2(4) + \sqrt{9}-8$

12. $3(7) + \sqrt{25} + 21$

13. $8(3) - \sqrt{36} + 15-2$

14. $19 + \sqrt{144}-22$

15. $3(4) + \sqrt{64} + \sqrt{25}$

### Vocabulary Language: English

Perfect Square

Perfect Square

A perfect square is a number whose square root is an integer.
Radical

Radical

The $\sqrt{}$, or square root, sign.
Radical Expression

Radical Expression

A radical expression is an expression with numbers, operations and radicals in it.
Rationalize the denominator

Rationalize the denominator

To rationalize the denominator means to rewrite the fraction so that the denominator no longer contains a radical.
Square Number

Square Number

A square number or perfect square is a whole number that is the square of another integer. For example, 36 is a square number because $6 \cdot 6 = 36$.
Variable Expression

Variable Expression

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

At Grade

Dec 21, 2012

## Last Modified:

Mar 22, 2015
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