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Mathematics 7 Online
OpenStudy (anonymous):

Care to help with Liberal Arts Math?

OpenStudy (anonymous):

Find the answer to \[\sqrt{169} * \ \frac{ 5 }{ 8}\] is the product nonzero, rational or irrational.

OpenStudy (anonymous):

My answer was \[\frac{ 5 }{ 8} \sqrt{13}\] rational

OpenStudy (anonymous):

@whpalmer4 Do you think it is correct or should i try again?

OpenStudy (whpalmer4):

That's not correct. Close, but not quite.

OpenStudy (whpalmer4):

what is the square root of 169?

OpenStudy (anonymous):

13

OpenStudy (anonymous):

so when i multiply 13 and 5/8 i get 8.125...

OpenStudy (whpalmer4):

I would leave it as a fraction, myself, but no matter. your error was that you replaced \(\sqrt{169}\) with \(\sqrt{13}\) instead of \(13\) \[\sqrt{169}*\frac{5}{8} = 13*\frac{5}{8} = \frac{65}{8} = 8\frac{1}{8}\]

OpenStudy (anonymous):

ah! so it would be rational!

OpenStudy (whpalmer4):

and \[8\frac{1}8 = 8.125\]so your calculator work is correct

OpenStudy (anonymous):

should I leave it as a fraction?

OpenStudy (whpalmer4):

yes, if you can get rid of the square root sign, it will be rational. if you're stuck with a square root sign, it is irrational.

OpenStudy (anonymous):

Care to check my other questions for me? there are not a lot. :)

OpenStudy (whpalmer4):

The problem doesn't say whether you need to express your answer in a particular form, so either way should be okay, but I generally prefer to stay with fractions unless I need decimals. And you could end up with something that doesn't have a fixed length decimal, like 1/3, where writing out the decimal is inconvenient at best...

OpenStudy (whpalmer4):

I could check a few...

OpenStudy (anonymous):

Thank you. Okay here is another. it ask to simplify then to write it in radical form for this I got the answer, \[6x^4\sqrt[11]{y^4}\]

OpenStudy (whpalmer4):

well, first of all, does your assignment say anything about the range of values that \(x\) and \(y\) can have?

OpenStudy (anonymous):

No all it ask is to simplify it and then rewrite it in the radical form.

OpenStudy (whpalmer4):

well, it matters because if you don't know what possible values your variables can take on, you can't do some simplifications. For example, you might think that\[\sqrt{x^2} = x\]right?

OpenStudy (anonymous):

You would combine the Y's correct?

OpenStudy (whpalmer4):

It seems like it works... \[x =3 \]\[x^2 = 9\]\[\sqrt{9} = 3\] but what if \(x = -1\)? \[x = -1\]\[x^2 = (-1)(-1) = 1\]\[\sqrt{1} = 1\]\[1 = -1\]uh...not really

OpenStudy (anonymous):

Hmm, still confused.

OpenStudy (whpalmer4):

well, probably if you're just starting this, they aren't bothering with such niceties...but strictly speaking, we can't do much simplification on this problem unless we know (or assume) that both \(x\) and \(y\) are not negative. so, I guess we'll assume that, and you can ask your teacher about whether or not you can simplify if the variables might be negative :-)

OpenStudy (anonymous):

let me list the choices.

OpenStudy (whpalmer4):

the original expression to simplify is \[x^{\frac{5}{3}}\cdot 6\sqrt[3]{x^7}\cdot y^{\frac{3}{4}}\cdot y^2\]did I get that right?

OpenStudy (anonymous):

yes it says to simplify then rewrite in radical form

OpenStudy (anonymous):

this is application of exponents.

OpenStudy (whpalmer4):

right...can you tell me how to write the term that starts with a 6 as an exponent form, like the other 3 product terms?

OpenStudy (anonymous):

Let me list the other choices.

OpenStudy (whpalmer4):

I don't need the other choices...we'll work through this and get the correct answer.

OpenStudy (anonymous):

A.\[6x^3\sqrt[9]{x^8}\sqrt{y^3}\] B.\[6\sqrt[9]{x^35}\sqrt[3]{y^2}\] C.\[6x^4y^2\sqrt[4]{y^3}\] D. \[6x^4\sqrt[11]{y^4}\]

OpenStudy (anonymous):

Ah sorry lol well working through it I know you need to combine the x and the y values.

OpenStudy (whpalmer4):

once more: can you tell me how to write the term that starts with a 6 as an exponent form, like the other 3 product terms?

OpenStudy (anonymous):

ah! you make it \[6x^ \frac{ 7 }{ 3}\]

OpenStudy (whpalmer4):

good. okay, can you combine the two product terms featuring \(x\)?

OpenStudy (anonymous):

yes! with the fractions you add them correct?

OpenStudy (whpalmer4):

\[x^a*x^b = x^{a+b}\]

OpenStudy (anonymous):

so it becomes \[x^\frac{ 12 }{ 3 }\]

OpenStudy (anonymous):

and that becomes 4 correct?

OpenStudy (whpalmer4):

yes. as long as \(x>0\) we can do that simplification, although ideally, we won't lose the \(6\) in the process :-)

OpenStudy (anonymous):

so it is 6x^4

OpenStudy (anonymous):

now we have Y

OpenStudy (anonymous):

so for both of them it would be \[y^ \frac{ 3 }{ 4 } * y ^2\]

OpenStudy (whpalmer4):

yes, and that combines to ...

OpenStudy (anonymous):

\[y ^\frac{ 6}{ 4 }\]

OpenStudy (anonymous):

or am i wrong?

OpenStudy (whpalmer4):

\[2 + \frac{3}{4} = \frac{6}{4}\]?

OpenStudy (anonymous):

hmm..

OpenStudy (whpalmer4):

$2 + $0.75 = $1.50? :-)

OpenStudy (anonymous):

OH!

OpenStudy (anonymous):

11/4

OpenStudy (whpalmer4):

you multiplied the exponents instead of adding them, I believe...

OpenStudy (whpalmer4):

there you go how would you write that as a radical expression?

OpenStudy (anonymous):

\[\sqrt[11]{y^4}\]

OpenStudy (whpalmer4):

yep, again, assuming that \(y>0\) so if we combine all the pieces, what is the final answer?

OpenStudy (anonymous):

D. aka \[6x^4\sqrt[11]{y^4}\]

OpenStudy (anonymous):

Yay so i was right!! Mind if I write this all down ^^

OpenStudy (whpalmer4):

whoops, sorry, that's not right. \[y^{\frac{11}{4}} = \sqrt[4]{y^{11}}\]

OpenStudy (whpalmer4):

but you can simplify that further by factoring out \(y^2\): \[y^{\frac{11}{4}} = y^{\frac{8}4}*y^{\frac{3}{4}} = y^2*y^{\frac{3}{4}} = y^2\sqrt[4]{y^3}\]

OpenStudy (anonymous):

ah okay lemme jot this down

OpenStudy (anonymous):

Thank you :)

OpenStudy (anonymous):

Now i understand it!!

OpenStudy (whpalmer4):

excellent!

OpenStudy (whpalmer4):

so the correct answer is C, not D

OpenStudy (anonymous):

alright sounds good.

OpenStudy (anonymous):

Im gonna continue with the others, I will let you know what I got. :)

OpenStudy (anonymous):

Okay for this one, it is like the first one, it says to find the answer to 0.2333333...etc. + the square root of 80. For this i got \[\sqrt{80}\] \[4\sqrt{5}\]

OpenStudy (anonymous):

and then for 0.23 i got \[\frac{ 23 }{ 99}\]

OpenStudy (anonymous):

now im confused is it rational or irrational

OpenStudy (whpalmer4):

well, first, 0.2333... is not \(23/99\) because \(23/99 = 0.23232323...\)

OpenStudy (whpalmer4):

but if you have radical sign in your expression and cannot simplify it away, you have an irrational number.

OpenStudy (anonymous):

Ah okay thank you

OpenStudy (whpalmer4):

\(\sqrt{2}\) irrational \(\sqrt{3}\) irrational \(\sqrt[4]\) rational, because you can simplify it to \(2\) \(\sqrt{5}\) irrational \(\sqrt{6}\) irrational etc.

OpenStudy (whpalmer4):

whoops, bumbled the typesetting there, but I think you can figure out what i meant :-)

OpenStudy (anonymous):

ah alright, okay for this one, its \[\frac{ 5 }{ 6 }\sqrt{180}\]

OpenStudy (anonymous):

I have no idea what to do here.

OpenStudy (whpalmer4):

factor the 180. does it turn into something made up entirely of perfect squares? for example: \[\sqrt{4} = \sqrt{2*2} = 2\]\[\sqrt{16} = \sqrt{2*2*2*2} = \sqrt{2*2}*\sqrt{2*2} = 2*2 = 4\]

OpenStudy (anonymous):

how about 25 and the sqrt of 26

OpenStudy (anonymous):

nope that seems to be 130...

OpenStudy (whpalmer4):

\[180 = 2*90 = 2*2*45 = 2*2*3*15 = 2*2*3*3*5 \]right? so \[sqrt{180} = \sqrt{2*2 * 3*3 * 5} = 2*3*\sqrt{5}\]rational or irrational?

OpenStudy (whpalmer4):

bah, more sloppy typesetting

OpenStudy (anonymous):

5(sqrt)5 over 6?

OpenStudy (whpalmer4):

\[\frac{5}{6}\sqrt{180} = \frac{5}{6}*\sqrt{2*2*3*3*5} = \frac{5}{6}*2*3\sqrt{5} = \frac{5}{\cancel{6}}*\cancel{2*3}\sqrt{5} = \]

OpenStudy (anonymous):

Still confused. i dont see the sqrt of 5 as the answer...from the choices.

OpenStudy (whpalmer4):

what are the choices? note my answer is not just the square root of 5...

OpenStudy (whpalmer4):

it is \[5\sqrt{5}\]

OpenStudy (anonymous):

A. 25(sqrt)25 over 6 irrational B. 5(sqrt)5 over 6 rational C.30(sqrt)5 rational D.5(sqrt)5 irrational

OpenStudy (anonymous):

So i was correct?

OpenStudy (anonymous):

\[5+\sqrt{98}\] is the next one. let me give you the answer i got.

OpenStudy (whpalmer4):

no, you were not. look at what I did. \[\frac{5}{6}\sqrt{180} = \frac{5}{6}\sqrt{2*2*3*3*5} = \frac{5}{6}*2*3*\sqrt{5} = \frac{5}{6}*6*\sqrt{5}\] what is \[\frac{5}{6}*6=\]

OpenStudy (anonymous):

just 5

OpenStudy (anonymous):

@whpalmer4 that would be 5 correct? so is D the correct answer?

OpenStudy (whpalmer4):

yes, D is the correct answer. and it is irrational because of that \(\sqrt{5}\)

OpenStudy (anonymous):

woo! Awesome sorry if Im being a burden. just gets confusing sometimes.

OpenStudy (whpalmer4):

nah, not a burden.

OpenStudy (whpalmer4):

if we do a good job today, that's zillions of questions I don't have to help on in the future, right? :-)

OpenStudy (anonymous):

Okay for the one with \[5+\sqrt{98}\] I seemed to have gotten \[12\sqrt{2}\] irrational and yep! that is correct!

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