newatthis
Multiply and simplify Radical Expression
1/2√5(1 1/2√20)
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newatthis
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|dw:1370239174862:dw|
newatthis
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Hi I got the answer of 7/2√5 but when I do it I get something different.
yummydum
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okay so lets write that a little prettier to deal with:\[{{1\over2}\sqrt{5}}\times{1~{1\over2}\sqrt{20}}~~\implies~~{{1\over2}\sqrt{5}}\times{{3\over2}\sqrt{20}}~~\implies~~{\sqrt{5}\over2}\times{3\sqrt{20}\over2}\]now that that looks a little better, let's solve:\[{{\sqrt{5}\times3\sqrt{20}}\over2}={3\sqrt{100}\over2}\]because 5 x 20 = 100\[3(10)\over2\]i think you've got it from here :)
yummydum
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oh i meant to write \[3(10)\over4\]sorry
newatthis
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I'm a bit lost I have to simplify this so would'nt 1 1/2√20 be 2 3/2√5
yummydum
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\[1 {1\over2} = {3\over2}\]\[\sqrt{20}= 2\sqrt{5}\]\[{3\over2}\times{2\over1}\sqrt{5}~~=~~{3\over\cancel{2}}\times{\cancel{2}\over1}\sqrt{5}~~=~~\large3\sqrt{5}\]
newatthis
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but the answer comes out to \[\frac{ 7 }{ 2 }\sqrt{5}\]
yummydum
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and where are you getting this from?
newatthis
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Our teacher placed the answer as \[\frac{ 7 }{ 2 }\sqrt{5}\]
newatthis
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I didn't get this answer either this is why it's confusing
yummydum
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1/2 times 3/2 = 3/4
sqrt 5 times sqrt 20 = sqrt100 = 10
3/4 times 10 = 7.5
i dont know what your teacher was doing, maybe you copied the question wrong
newatthis
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No it's printed on my paper
yummydum
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then im really not sure
newatthis
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I appreciate your help Thank you yummydum
yummydum
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no problem :)
newatthis
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I got as my final answer \[\frac{ 3 }{ 4 }\sqrt{5} \] this is why it was confusing
newatthis
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I had a person help me don't I don't believe it's correct here is why unless I'm wrong
saifoo.khan
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Alright so i read the whole problem. Where are you stuck? We should get 15/2.
newatthis
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\[1\frac{ 1 }{ 2 }\sqrt{20}\] would be \[\frac{ 3 }{ 2 }\] and \[\sqrt{20} would be 2\] add both \[2\frac{ 3 }{ 2 }\sqrt{5}\]
newatthis
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teacher has an answer of \[\frac{ 7 }{ 2 }\sqrt{5}\] could the teacher be wrong
saifoo.khan
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Yes. Teacher added the sqrt5 by misatke. Or maybe the question you wrote is incorrect.
newatthis
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question is multiply and simplify \[\frac{ 1 }{ 2 }\sqrt{5}\left( 1\frac{ 1 }{ 2 } \sqrt{20}\right)\]
saifoo.khan
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|dw:1370243682678:dw|
newatthis
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Why is this so complicated? I'm lost
saifoo.khan
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Which step is it that you don't understand?
newatthis
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how would I multiply \[\frac{ \sqrt{5} }{ 2 }\times \frac{ 3*2 }{ 2 }\sqrt{5}\] I thought you multiply numbers not square roots with numbers
newatthis
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my answer was \[\frac{ 3 }{ 4 }\sqrt{5}\] maybe this is wrong
saifoo.khan
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|dw:1370244388921:dw|
newatthis
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Wouldn't we keep the root? and just multiply getting \[\frac{ 15 }{ 2 }\sqrt{5}\]
saifoo.khan
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No ma'am.
Whenever it's given:
sqrt3 * sqrt3
we will get "3" as answer.
The roots cancel out leaving you with ONE three.
newatthis
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This is how I started
\[\frac{ 1 }{ 2 }\sqrt{5}(1\frac{1 }{ 2 }\sqrt{20})\]
\[\frac{ 1 }{ 2 }\sqrt{5}(\frac{3 }{ 2 }\sqrt{5})\]
\[\frac{ 1 }{ 2 }\times \frac{ 3 }{ 2 }=\frac{ 3 }{ 4 }\sqrt{5}\]
I know this isn't corrected but I get this
saifoo.khan
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How will you simplify sqrt 20?
newatthis
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that's right it would be 4*5 which 4 goes down to 2 so it would be \[2\sqrt{5}\]
saifoo.khan
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^
newatthis
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I forgot to add that
\[\frac{ 1 }{ 2 }\sqrt{5}(2\frac{3 }{ 2 }\sqrt{5})\]
it would be this correct and mix fractions to improper fractions would be \[2\frac{ 3 }{ 2 } would be \frac{ 7 }{ 2 }\]
\[\frac{ 1 }{ 2 }\sqrt{5}(\frac{ 7 }{ 2 }\sqrt{5})\]
saifoo.khan
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You made a mistake again. :P
It's not 2 3/2
newatthis
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so it's \[\frac{ 2 }{ 1 }X\frac{ 3 }{ 2 }\]
saifoo.khan
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No.
I think you should redo the problem. Show me yor steps please.
newatthis
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ok
newatthis
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\[\frac{ 1 }{ 2 }\sqrt{5}(1\frac{ 1 }{ 2 }\sqrt{20})\]
\[\frac{ 1 }{ 2 }\sqrt{5}(\frac{ 3 }{ 2 } 2\sqrt{5})\]
\[\frac{ 1 }{ 2 }\sqrt{5}(\frac{ 3 }{ 2 } 2\sqrt{5})\]
at this point I'm lost
saifoo.khan
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Awesome.
No the 2's on right cancels out. Right?
newatthis
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why would it cancel √20 would be 2√5 this is where I'm getting confused
newatthis
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is 2 canceling with the other 2
saifoo.khan
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sqrt(20) = sqrt(2*2*5) = 2 sqrt5
Agree?
newatthis
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yes
saifoo.khan
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Now the 2 from 2sqrt5 and the w in the denominator on the right canel out
newatthis
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I'm with you on that
saifoo.khan
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Right o what are we left with now?
newatthis
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3√5
saifoo.khan
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Right. And that is multiplied with..?
newatthis
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\[\frac{ 1 }{ 2 }\sqrt{5}\]
saifoo.khan
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Right now multiply it out.
newatthis
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\[\frac{ 1 }{ 2 }\sqrt{5}\times \frac{ 3 }{ 1 }\sqrt{5}\]
Is this looking correct?
saifoo.khan
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yes
newatthis
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\[\frac{ 3 }{ 2 }\sqrt{5}\]
newatthis
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do I take of the √ and make it \[\frac{ 3 }{ 2 }\times \frac{ 5 }{ 1 }=\frac{ 15 }{ 2 }\]
saifoo.khan
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Like a boss. (y)
newatthis
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Thanks for everything wow :.)
help123please.
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Good job helping @newatthis !!!
@saifoo.khan
help123please.
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Kudos to @yummydum too!
saifoo.khan
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@yummydum is useless.
help123please.
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No she isn't :p
help123please.
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I'M useless.
help123please.
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Yummydum isn't. Or you,for that matter.
newatthis
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Thanks for everything it helps a lot when someone knows how to guide and explain it. :)
saifoo.khan
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@help123please. believe me. I know her.
@newatthis You're welcome. :)
help123please.
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Well,yes...you've been here longer than me.
saifoo.khan
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Lol. But no doubt she has a brown brain like me! D:
help123please.
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O_O
help123please.
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Yours is a great brain,Saif.
help123please.
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U ARE 2 HELPFUL. Lol.
saifoo.khan
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And it's brown too!
help123please.
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Nope it's not.
saifoo.khan
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I'm brown. Brain is brown too. Dummy is brown too. Hence she has a brown brain too.
help123please.
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We're prolly weirding @newatthis out.
Or at least,I am.
help123please.
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:P
help123please.
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'Hence,she has a brown brain too'.
Hence. I like that word.
saifoo.khan
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Lol.
newatthis
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no I'm just doing math working my brain, or whatever is left. :)
help123please.
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Saif,I just noticed your smartscore is mine,with the numbers flipped upside down. XD
saifoo.khan
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Haha. Nice catch.
help123please.
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IKR.
help123please.
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*Flips PC upside down*
OMGEE I HAVE A 99 SS!
saifoo.khan
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Lol.
help123please.
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98% of the time,when typing lol,you're not actually laughing. Did u know? :P
saifoo.khan
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Make that 99%. I love laughing. It helps in exercising my face muscles. :P
help123please.
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Lawl.
saifoo.khan
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;)
newatthis
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so new question?
\[2x \sqrt{7}(3x \sqrt{7})\]
\[2x(3x)\sqrt{7}\sqrt{7}\]
\[6x(\sqrt{49})\]
Would this be correct?
newatthis
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sorry I just threw this in here
help123please.
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@newatthis please close this post and create a new thread.
yummydum
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2x * 3x = 6x^2 not just 6x
and √49 = 7
so now you have 6x^2 * 7 ....which is?
newatthis
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\[42x ^{2}\]
yummydum
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yes