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Mathematics 7 Online
OpenStudy (anonymous):

need help with algebra, thanks!

OpenStudy (anonymous):

\[\frac{ 4 \sqrt{6} }{ \sqrt{30}} \]

OpenStudy (anonymous):

simplify by rationalizing the denominator. Show work

OpenStudy (mrnood):

You posted this elsewhere Multiply the numerator by sqrt(6)

OpenStudy (mrnood):

soz - AND numerator

OpenStudy (mrnood):

oops! and denominator

OpenStudy (anonymous):

so 9.79 is 4 times sqr6?

OpenStudy (mrnood):

forget the calculator for now - just multiply top and bottom by sqrt(6)

OpenStudy (anonymous):

so it is 4 sqr6 * sqrt6/sqrt30*sqrt6

OpenStudy (mrnood):

AND SQRT(6)*SQRT(6) =?? And sqrt (30)*sqrt(6) =??

OpenStudy (anonymous):

first: 6 second=13.4

OpenStudy (shiraz14):

@Darealest123: You do not rationalize the numerator - you rationalize the denominator. So, instead of multiplying by sqrt(6) on both the numerator and the denominator, you will choose to multiply by the radical on the denominator [i.e. sqrt(30)]. And the 13.4 you got earlier is an estimate, which is why we never rationalize the numerator.

OpenStudy (mrnood):

forget the calculator - stick with the formula sqrt(30)*sqrt(6) = sgrt(???)

OpenStudy (anonymous):

Do i just multiply the numbers and leave the sqrt

OpenStudy (mrnood):

yes then 180 = 9*4*5

OpenStudy (anonymous):

and what do i do with that?

OpenStudy (mrnood):

9 and 4 are squares - so you can simplify the sqrt HOWEVER - @shiraz14 is correct - Start again and multiply top and bottom by sqrt (30) )(Sorry!)

OpenStudy (anonymous):

4 sqrt 6 * sqrt30?

OpenStudy (mrnood):

You have missed off the denominator in your above post.... you will still end up with sqrt(9*4*5) Since 9 and 4 are squares you can simplify

OpenStudy (anonymous):

Sooooo... i multiply 9*4 because they are squares

OpenStudy (anonymous):

I don't understand what you mean by simplify. If possible when your done you could show me in like bullet points the steps you took because this seems simple but not to me because i don't understand this stuff

OpenStudy (mrnood):

No - you multiply by the denominator - to remove the sqrt in the denominator The top then becomes 4 * sqrt (180) You then need to look at the factors of 180 - I have done it for you 9*4*5 Sqrt(180)=sqrt(9)*sgrt(4)*sqrt(5) After simplifying - the only sqrt you are left with is sqrt(5)

OpenStudy (anonymous):

so denominator is sqrt 5

OpenStudy (anonymous):

?\[4\times \sqrt{180}/ \sqrt{5}\]

OpenStudy (anonymous):

@MrNood

OpenStudy (mrnood):

You need to do this for yourself to understand it - your post shows that oyu are not thinking about it. a) multiply top and bottom by sqrt (30) b) join the 2 sqrt terms on the top into 1 c) factorise the new term on the top d) Simplify the factors under the sqrt on numerator (I gave you the answer above) Simplify the 2 sqrt terms in the denominator (they are both sqrt(30)) e) complete the equation Take it slowly - write the WHOLE equation at all stages

OpenStudy (anonymous):

So i multiply both sides by sqrt 30 which would give me 4*sqrt180/189x*sqrt30 then im not sure what to do with the next question

OpenStudy (mathstudent55):

The idea of rationalizing a denominator is to not have any radicals in the denominator. In this case, some simplification can be done before rationalizing the denominator. \(\dfrac{4 \sqrt{6}}{\sqrt{30}} \) First we simplify: \(= \dfrac{4 \sqrt{6}}{\sqrt{5}\sqrt{6}} \) \(= \dfrac{4 \cancel{\sqrt{6}}}{\sqrt{5}\cancel{\sqrt{6}}} \) \(=\dfrac{4}{\sqrt{5}} \) Now we rationalize: \(=\dfrac{4}{\sqrt{5}} \times \dfrac{\sqrt5}{\sqrt5} \) \(=\dfrac{4\sqrt5}{\sqrt{25}} \) \(=\dfrac{4\sqrt5}{5} \)

OpenStudy (anonymous):

so 4sqrt 5/5 is all the way down because you are rationalizing the denominator

OpenStudy (mathstudent55):

Of course, if you didn't realize that you can simplify the fraction before rationalizing, you should arrive at eh same result. \(\dfrac{4 \sqrt{6}}{\sqrt{30}} \) \(=\dfrac{4 \sqrt{6}}{\sqrt{30}} \times \dfrac{\sqrt{30}}{\sqrt{30}} \) \(=\dfrac{4 \sqrt{180}}{\sqrt{900}} \) \(=\dfrac{4 \sqrt{36 \times 5}}{30} \) \(=\dfrac{4 \sqrt{36} \sqrt{5}}{30} \) \(=\dfrac{4 \times 6 \times\sqrt{5}}{6 \times 5} \) \(=\dfrac{4 \times \cancel6 \times\sqrt{5}}{\cancel6 \times 5} \) \(=\dfrac{4 \sqrt{5}}{5} \) As expected, the answer is the same.

OpenStudy (anonymous):

Thank you so much you are awesome i gave fan and medal i think :)

OpenStudy (mathstudent55):

Notice that in \(\dfrac{4 \sqrt{5}}{5}\) there is no radical in the denominator. That is the goal of rationalizing a denominator.

OpenStudy (mathstudent55):

You're welcome & thanks.

OpenStudy (mrnood):

since @mathstudent55 gave you the answer straight out I assume you have fully understood it now!"

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