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Mathematics 20 Online
OpenStudy (18jonea):

Rationalize the denominator of https://api.agilixbuzz.com/Resz/~Ey6YBAAAAAA81ZXByil0iA.RBcymAkaS7gygkcdGLtgrA/19809088,B87/Assets/assessmentimages/alg%202%20pt%202%20u3l8%2011.jpg @wolf1728 @thesmartone

OpenStudy (18jonea):

@zzr0ck3r

OpenStudy (18jonea):

@whpalmer4

OpenStudy (zzr0ck3r):

multiply top and bottom by \(2+\sqrt{6}\)

OpenStudy (18jonea):

is it 2-

OpenStudy (18jonea):

@zzr0ck3r

OpenStudy (18jonea):

i thought you multiply the denominator

OpenStudy (18jonea):

\[4-\sqrt{6}\] i got this for numerator but don't know what to do now @TheSmartOne

OpenStudy (18jonea):

@agent0smith

OpenStudy (18jonea):

@Zarkon

OpenStudy (18jonea):

@pooja195

OpenStudy (18jonea):

@Kainui

OpenStudy (mjdennis):

Describe to me what you did, and where your answer is so far.

OpenStudy (18jonea):

i multiplied the denominator and numerator

OpenStudy (18jonea):

@mjdennis

OpenStudy (18jonea):

@Jaynator495

OpenStudy (18jonea):

@rebeccaxhawaii

OpenStudy (18jonea):

@zepdrix

OpenStudy (18jonea):

@TheSmartOne

OpenStudy (mjdennis):

I don't understand "multiplied the denominator and numerator" Did you multiply them together? Did you multiply them both by one thing?

OpenStudy (mjdennis):

OK, let's start over. Simplify 2 + √6 ------ 2 - √6 Right?

OpenStudy (18jonea):

\[\frac{ 2+\sqrt{6} }{ 2-\sqrt{6} } \times \frac{ 2-\sqrt{6} }{ 2-\sqrt{6} }\]

OpenStudy (mjdennis):

OK, that was close. You really need to use 2 + √6. I think you will see why that is better when you do it

OpenStudy (mjdennis):

Sorry, I mean 2 + √6 on both top AND bottom. One sec, I will put it in the equation editor.

OpenStudy (mjdennis):

\[\frac{ 2+\sqrt{6} }{2-\sqrt{6} } \times \frac{ 2+\sqrt{6} }{2+\sqrt{6} }\]

OpenStudy (18jonea):

ok so what do i do now?

OpenStudy (18jonea):

@mjdennis

OpenStudy (mjdennis):

This is the same as: \[\frac{ (2+\sqrt{6}) \times (2+\sqrt{6}) }{ (2-\sqrt{6}) \times (2+\sqrt{6}) }\]

OpenStudy (mjdennis):

So do those two multiplications out

OpenStudy (18jonea):

\[\frac{ 4+\sqrt{36} }{ 4-\sqrt{36} }\]

OpenStudy (18jonea):

is that right?

OpenStudy (mjdennis):

The denominator is right. The numerator is the form (a+b)(a+b) = a^2+2ab+b^2, so try the numerator again,please.

OpenStudy (18jonea):

im not really sure what that means?

OpenStudy (mjdennis):

it means when you multiply (2+√6)×(2+√6), you have to add _four_ terms: (2×2) (2×√6) (√6 × 2) (√6 × √6) and add those up.

OpenStudy (18jonea):

4 2sqrt6 2sqrt6 6

OpenStudy (18jonea):

is that right?

OpenStudy (mjdennis):

Yes, but add them up. You may want to practice multiplying mixed numbers (like 2+√6) some more.

OpenStudy (mjdennis):

Youw ill need that skill more in math.

OpenStudy (mjdennis):

Ha, sorry, "You will.."

OpenStudy (mjdennis):

@18jonea , I'll hang out a bit in case you come back.

OpenStudy (18jonea):

im back sorry had to get a snack

OpenStudy (mjdennis):

NP. Gotta stay fueled up.

OpenStudy (18jonea):

4.89897948557 i got this for 2 square root 6

OpenStudy (mjdennis):

Not sure how you are supposed to put the answer. Does the problem say?

OpenStudy (mjdennis):

I would have left the √6 alone in my answer.

OpenStudy (18jonea):

o ok

OpenStudy (mjdennis):

Let's follow that through, just in case, then you also have that answer.

OpenStudy (18jonea):

-5 -1 \[-5-2\sqrt{6}\] \[-\frac{ 5 }{ 2}-\sqrt{6}\]

OpenStudy (18jonea):

are my options

OpenStudy (mjdennis):

4+6 is 10, but I figure you got that part. 2√6 +2√6 is 4√6, right? So the top is 10+√6

OpenStudy (18jonea):

yes

OpenStudy (mjdennis):

The bottom was 4-√36 . Can you reduce that?

OpenStudy (18jonea):

\[\sqrt{6}\]

OpenStudy (18jonea):

sorry just 6

OpenStudy (mjdennis):

Did you mean 4-6? That reduces further still.

OpenStudy (18jonea):

-2

OpenStudy (mjdennis):

Oops. Top should have been 10+4√6 I'll re do it

OpenStudy (18jonea):

d?

OpenStudy (mjdennis):

Put them back together and we are almost done: \[\frac{ 10+4\sqrt{6} }{ -2 }\] and you can use distribution to split the -2 over both halves: \[\frac{ 10 }{ -2 } + \frac{ 4\sqrt{6} }{ -2 }\] Can you bring it home? Only one match among your choices.

OpenStudy (mjdennis):

Not d

OpenStudy (18jonea):

c

OpenStudy (mjdennis):

I guess. You didn't label the choices!

OpenStudy (18jonea):

\[-5-2\sqrt{6}\]

OpenStudy (18jonea):

@mjdennis

OpenStudy (mjdennis):

Wait, I helped you through all the tough stuff, and you would like me to believe that you cannot divide 10 by -2, or divide 4√6 by -2 , and be confident in the answer?

OpenStudy (18jonea):

-5 is the 10

OpenStudy (mjdennis):

So, I think you got it from here.

OpenStudy (18jonea):

just dont know the square root

OpenStudy (18jonea):

im 99% sure it is c

OpenStudy (mjdennis):

OK. Right, 10/(-2) is -5. Only one answer had -5, so be confident in that. When we write √6, we are using "√6" as a symbol. It stands in for an number a little bigger than 2.449 and a little smaller than 2.450. So we can just treat it as any other number, but leave it as a symbol. Suppose I asked you to find 20/-2 ? You could say "20 is 2*10, and I know 10/-2 is -5, so 20/-2 is twice -5, so 20/-2 is -10. Same for 4√6/-2. It is =2√6. We never have to touch the √6, because it is the simplest form.

OpenStudy (mjdennis):

Good luck! Gotta go.

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