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Mathematics 19 Online
OpenStudy (anonymous):

can anybody please help me with this?

OpenStudy (anonymous):

OpenStudy (phi):

you should do this: factor each number inside the square roots into their "prime factors" distribute the \( \sqrt{13}\) (multiply it times each term inside the parens) use the rule \[ \sqrt{a}\cdot \sqrt{b} = \sqrt{a\cdot b} \] but don't actually multiply the numbers, just combine them inside one square root now look for pairs to pull out of the square root.

OpenStudy (anonymous):

\[6\sqrt{2} \times \sqrt{13} \times \sqrt{2}\]

OpenStudy (anonymous):

@phi I distributed and got this. Is this correct?

OpenStudy (phi):

when you distribute, you have to keep the plus sign between the two terms

OpenStudy (phi):

this is a multi - step problem \[ \left(\sqrt{72} + \sqrt{26} \right)\sqrt{13}\] distribute means multiply the sqrt(13) times each term inside the parens Just write \(\sqrt{13}\) next to each term inside the parens. can you do that ?

OpenStudy (anonymous):

\[\sqrt {13} (\sqrt{72}) + \sqrt {13} (\sqrt {26})\] like this?

OpenStudy (phi):

yes next we use this rule on both terms \[ \sqrt{a}\sqrt{b}= \sqrt{a\cdot b}\] all that means is change \( \sqrt{13} \sqrt{72} \) into \(\sqrt{13\cdot 72} \) do that for both terms. can you do that ?

OpenStudy (anonymous):

\[\sqrt {13 \times 72} + \sqrt {13 \times 16}\]

OpenStudy (anonymous):

like this?

OpenStudy (phi):

you mean 26 not 16 in the 2nd term, right ?

OpenStudy (anonymous):

yes sorry 26*

OpenStudy (phi):

now factor the 72, because we want to find pairs can you do that ?

OpenStudy (anonymous):

\[6 \times \sqrt {2}\]

OpenStudy (anonymous):

right?

OpenStudy (phi):

for the first term, you start with \[ \sqrt{13 \cdot 72 }\] if we factor 72 into 2*36 = 2*6*6 we have \[ \sqrt{13 \cdot 2\cdot 6 \cdot 6 }\] now pull out the pair of 6's what do you get ?

OpenStudy (anonymous):

\[\sqrt {13 \times 2}\]

OpenStudy (anonymous):

right?

OpenStudy (phi):

yes, but with a 6 out front... (the pair of 6's come out of the radical, and one of the 6's goes in front. try again

OpenStudy (anonymous):

\[6 \sqrt {13 \times 2}\]

OpenStudy (phi):

yes. and now can you simplify the 2nd term \[ \sqrt{13\cdot 26} \]

OpenStudy (phi):

factor the 26 into 2*13 \[ \sqrt{13 \cdot 2 \cdot 13} \] now pull out a pair (and put one of them out front )

OpenStudy (anonymous):

\[13 \sqrt {2}\]

OpenStudy (phi):

so now you have \[ 6 \sqrt{13 \cdot 2 } + 13 \sqrt{2} \] you can not do any more with this except multiply the 13*2 inside the radical \[ 6 \sqrt{26 } + 13 \sqrt{2} \] that is the answer

OpenStudy (anonymous):

thank you SO MUCH!

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