Algebra II : Multiplying and Dividing Radicals

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #11 : Multiplying And Dividing Radicals

Solve and simplify.

\displaystyle \sqrt{9}\cdot \sqrt{3}

Possible Answers:

\displaystyle \sqrt{27}

\displaystyle 2\sqrt{3}

\displaystyle 27

\displaystyle 3\sqrt{3}

\displaystyle \sqrt{3}

Correct answer:

\displaystyle 3\sqrt{3}

Explanation:

When multiplying radicals, just take the values inside the radicand and perfom the operation.

In this case, we have a perfect square so simplify that first.

Then, take that answer and multiply that with \displaystyle \sqrt{3} to get the final answer.

\displaystyle {\sqrt{9}}\cdot \sqrt{3}=3\cdot \sqrt{3}=3\sqrt{3}.

 

Example Question #12 : Multiplying And Dividing Radicals

Solve and simplify.

\displaystyle \frac{\sqrt{5}}{\sqrt{3}}

Possible Answers:

\displaystyle \frac{\sqrt{3}}{5}

\displaystyle {\sqrt{15}}

\displaystyle 1

\displaystyle \frac{\sqrt{15}}{3}

\displaystyle \frac{5}{3}

Correct answer:

\displaystyle \frac{\sqrt{15}}{3}

Explanation:

When dividing radicals, check the denominator to make sure it can be simplified or that there is a radical present that needs to be fixed. Since there is a radical present, we need to eliminate that radical. To do this, we multiply both top and bottom by \displaystyle \sqrt{3}. The reason is because we want a whole number in the denominator and multiplying by itself will achieve that. By multiplying itself, it creates a square number which can be reduced to \displaystyle 3.

\displaystyle \frac{\sqrt{5}}{\sqrt{3}}\cdot \frac{\sqrt{3}}{\sqrt{3}}=\frac{\sqrt{15}}{\sqrt{9}}=\frac{\sqrt{15}}{3}

With the denominator being \displaystyle 3, the numerator is \displaystyle \sqrt{5\cdot 3}=\sqrt{15}. Final answer is \displaystyle \frac{\sqrt{15}}{3}.

 

 

 

Example Question #111 : Simplifying Radicals

Solve and simplify.

\displaystyle \frac{\sqrt{9}}{\sqrt{4}}

Possible Answers:

\displaystyle 1

\displaystyle \frac{3}{2}

\displaystyle \frac{{\sqrt{3}}}{\sqrt{2}}

\displaystyle \sqrt{13}

\displaystyle \frac{9}{4}

Correct answer:

\displaystyle \frac{3}{2}

Explanation:

When dividing radicals, check the denominator to make sure it can be simplified or that there is a radical present that needs to be fixed.

Both \displaystyle 9 and \displaystyle 4 are perfect squares so they can be simplify.

Final answer is

 \displaystyle \frac{\sqrt9}{\sqrt4}=\frac{\sqrt{3\cdot 3}}{\sqrt{2\cdot 2}}=\frac{3}{2}.

Example Question #11 : Multiplying And Dividing Radicals

Solve and simplify.

\displaystyle 3\sqrt{2}\cdot 4\sqrt{3}

Possible Answers:

\displaystyle 7\sqrt{5}

\displaystyle 6\sqrt{2}

\displaystyle 884

\displaystyle \sqrt{123}

Correct answer:

Explanation:

When multiplying radicals, just take the values inside the radicand and perfom the operation.

Since there is a number outside of the radicand, multiply the outside numbers and then the radicand.

\displaystyle 3{\sqrt{2}}\cdot 4\sqrt{3}=3\cdot 4\cdot \sqrt{2\cdot 3}=12\sqrt{6}

Example Question #112 : Simplifying Radicals

Solve and simplify.

\displaystyle 3\sqrt{6}\cdot 6\sqrt{10}

Possible Answers:

\displaystyle 18\sqrt{60}

\displaystyle 60\sqrt{18}

\displaystyle 36\sqrt{15}

\displaystyle 36

\displaystyle 15

Correct answer:

\displaystyle 36\sqrt{15}

Explanation:

When multiplying radicals, just take the values inside the radicand and perfom the operation.

Since there is a number outside of the radicand, multiply the outside numbers and then the radicand. 

\displaystyle 3\sqrt{6}\cdot 6\sqrt{10}=3\cdot 6\cdot\sqrt{6\cdot10}=18\sqrt{60}

Before we say that's the final answer, check the radicand to see that there are no square numbers that can be factored. A \displaystyle 4 can be factored and thats a perfect square. When I divide \displaystyle 60 with \displaystyle 4, I get \displaystyle 15 which doesn't have perfect square factors.

Therefore, our answer becomes

\displaystyle 18{\sqrt{60}}=18\sqrt{4\cdot 15}=18\cdot2\sqrt{15}=36\sqrt{15}

 

Example Question #12 : Multiplying And Dividing Radicals

Solve and simplify.

\displaystyle 2\sqrt{15}\cdot \sqrt{15}

Possible Answers:

\displaystyle 15\sqrt{15}

\displaystyle 15

\displaystyle 3\sqrt{15}

\displaystyle 30

\displaystyle 30\sqrt{15}

Correct answer:

\displaystyle 30

Explanation:

When multiplying radicals, just take the values inside the radicand and perfom the operation.

Since there is a number outside of the radicand, multiply the outside numbers and then the radicand. 

\displaystyle 2\sqrt{15}\cdot \sqrt{15}=2\cdot\sqrt{15\cdot15}=2\cdot15=30

 

Example Question #13 : Multiplying And Dividing Radicals

Solve and simplify.

\displaystyle (4\sqrt{7})^2

Possible Answers:

\displaystyle 112

\displaystyle 16

\displaystyle 784

\displaystyle 47

\displaystyle 28

Correct answer:

\displaystyle 112

Explanation:

Since we are dealing with exponents, lets break it down.

\displaystyle (4{\sqrt{7}})^2=4^2\cdot ({\sqrt{7}})^2=16\cdot 7=112

Remember to distribute.

Example Question #18 : Multiplying And Dividing Radicals

Solve and simplify.

\displaystyle \frac{\sqrt{24}}{\sqrt{2}}

Possible Answers:

\displaystyle 3\sqrt{2}

\displaystyle \sqrt{2}

\displaystyle 12

\displaystyle 3

\displaystyle 2\sqrt{3}

Correct answer:

\displaystyle 2\sqrt{3}

Explanation:

When dividing radicals, check the denominator to make sure it can be simplified or that there is a radical present that needs to be fixed. Since there is a radical present, we need to eliminate that radical. However, there is a faster way to possibly elminate the denominator. Let's simplify the numerator.

\displaystyle \sqrt{24}=\sqrt{8\cdot3}=\sqrt{4\cdot2\cdot3}=2\sqrt{2}\cdot\sqrt{3}.

The reason I split it up is because I can cancel out the radicals and thus simplifying the question to give final answer of \displaystyle 2\sqrt{3}.

Example Question #1452 : Mathematical Relationships And Basic Graphs

Solve and simplify.

\displaystyle \frac{2\sqrt{75}}{3\sqrt{175}}

Possible Answers:

\displaystyle \frac{7\sqrt{21}}{2}

\displaystyle 3

\displaystyle 3\sqrt{2}

\displaystyle \frac{2\sqrt{21}}{21}

\displaystyle 21

Correct answer:

\displaystyle \frac{2\sqrt{21}}{21}

Explanation:

When dividing radicals, check the denominator to make sure it can be simplified or that there is a radical present that needs to be fixed. Since there is a radical present, we need to eliminate that radical. However, there is a faster way to possibly elminate the denominator. Let's simplify the numerator.

\displaystyle \frac{2\sqrt{75}}{3\sqrt{175}}=\frac{2\cdot\sqrt{25\cdot3}}{3\cdot\sqrt{25\cdot7}}=\frac{2\cdot\sqrt{25}\cdot\sqrt{3}}{3\cdot\sqrt{25}\cdot\sqrt{7}}=\frac{2\sqrt{3}}{3\sqrt{7}}

We still need to eliminate the radical so multiply top and bottom by \displaystyle \sqrt{7}.

\displaystyle \frac{2\sqrt{3}\cdot\sqrt{7}}{3\sqrt{7}\cdot\sqrt{7}}=\frac{2\sqrt{21}}{3\cdot 7}=\frac{2\sqrt{21}}{21}.

Example Question #122 : Simplifying Radicals

Multiply and simplify:

\displaystyle \sqrt{12x}\cdot \sqrt{3x^4}.

Possible Answers:

\displaystyle x^2\sqrt{x}

\displaystyle 6x\sqrt{x}

\displaystyle 6x^2\sqrt{x}

\displaystyle \sqrt{x}

\displaystyle x^2\sqrt{6x}

Correct answer:

\displaystyle 6x^2\sqrt{x}

Explanation:

I would first multiply and put everything under the radical to then figure out what to simplify.

After mulitplying everything together, it should look like:

\displaystyle \sqrt{36x^5}.

Then, simplify.

\displaystyle 36 is a perfect square, and for every pair of x's, put one on the outside and cross out the pair.

We are left with an answer of:

\displaystyle 6x^2\sqrt{x}.

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