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Mathematics 12 Online
OpenStudy (anonymous):

Am I right?

OpenStudy (uri):

MAYBE.

OpenStudy (anonymous):

\[\sqrt[3]{32}\] This is the answer I ended with. \[8\sqrt{8}\]

OpenStudy (anonymous):

I think it is wrong, because I'm not sure what I'm supposed to do with the exponent :c

OpenStudy (uri):

Do you have answer choices?

OpenStudy (anonymous):

No, all I know is that I need to simplify the equation and the answer cannot be a decimal under any circumstances.

OpenStudy (anonymous):

No, that's not right. Remember that the perfect cubes are \[2^3 = 8\] \[3^3 = 27\] etc. So \[\sqrt[3]{32} = \sqrt[3]{ 8 \cdot 4} = \sqrt[3]{8} \cdot \sqrt[3]4 = ?\]

OpenStudy (anonymous):

So whenever there is an exponent on the outside I'm supposed to multiply the simplified version of 32?

OpenStudy (anonymous):

Okay--- You lost me Jem. I know that, you can only simplify 4 into a perfect square which would be 2... But would it be, 4^3 or not?

OpenStudy (anonymous):

You can't simplify the cube root of four, but you can certainly simplify the cube root of eight.

OpenStudy (anonymous):

Wait what--- 8 isn't a perfect square though? How is that possible?

OpenStudy (mathstudent55):

\(\sqrt[3]{32} \) \( = \sqrt[3] {2 \times 2 \times 2 \times 2 \times 2 } \) \( = \sqrt[3] {\color{red}{2 \times 2 \times 2}}~ \sqrt[3]{ \color{green}{2 \times 2} } \) \( = \color{red}2 ~ \sqrt[3]{ \color{green}4 } \)

OpenStudy (anonymous):

You're not talking about perfect squares, you're talking about perfect cubes.

OpenStudy (mathstudent55):

8 is a perfect cube which is what you need here since you are taking the cubic root.

OpenStudy (anonymous):

I never learned about that, so I don't know how to do it...

OpenStudy (anonymous):

It's exactly the same idea as a square root. \[2^2 = 2\cdot 2 = 4 \implies \sqrt{4} = 2\] \[2^3 = 2\cdot 2 \cdot 2 = 8 \implies \sqrt[3]8 = 2 \]

OpenStudy (anonymous):

So the answer is just 2?

OpenStudy (mathstudent55):

Answer is \(2\sqrt[3]{4} \)

OpenStudy (anonymous):

I wish I could give a medal to the both of you-- But, Jem helped first.. Sorrry Math

OpenStudy (mathstudent55):

@TheHero You are familiar with square roots. Can you simplify \(\sqrt{27}\) showing steps?

OpenStudy (anonymous):

Yes, that would be easy. \[\sqrt{27}\] \[\sqrt{3} \sqrt{9} = 3\sqrt{3}\]

OpenStudy (mathstudent55):

Thanks, but don't worry about the medal. The important thing is for you to understand this.

OpenStudy (mathstudent55):

Great. The reason you chose to factor 27 into 9 and 3 is that you are taking a square root, and 9 is a perfect square. When you take a cubic root, then you factor the number trying to take out the largest perfect cube. The number 32 = 2 * 2 * 2 * 2 * 2. If you take three factors of 2, 2 * 2 * 2 = 8, you have a perfect cube. Thats' why the number 32 was factored into 8 and 4. Since 8 is a perfect cube, the cubic root of 8 is 2. 4 is not a perfcet cube, so it remained inside the cubic root sign. This is similar to the problem \(\sqrt{27}\)you did correctly, where the 3 remained inside the square root and the \( \sqrt{9} \) came out as 3.

OpenStudy (anonymous):

Oh! I understand it now, thank you very much! c:

OpenStudy (mathstudent55):

For example, \( \sqrt[5] {729} \) \(= \sqrt[5] {3^6} \) \( =\sqrt[5]{3^5} ~ \sqrt[5] {3} \) \(=3 \sqrt[5]{3} \) Since this problem has a fifth root, you need to take out a perfect fith power number, 3^5.

OpenStudy (mathstudent55):

You're welcome.

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