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Geometry 18 Online
OpenStudy (anonymous):

Still need some more help!.. Sorry, but I have just a few more I believe!

OpenStudy (anonymous):

@whpalmer4 @Compassionate

OpenStudy (anonymous):

And anyone else that can help!!!

OpenStudy (whpalmer4):

please post the questions, then tag, not the other way around, thanks :-)

OpenStudy (anonymous):

sorry. Still new to this... ~ A square with a side of 20 is decreased to a side of 16. By how much is the diagonal decreased?

OpenStudy (whpalmer4):

Okay, our first square is 20 x 20. What is the diagonal? Draw a picture:|dw:1393990700727:dw|

OpenStudy (whpalmer4):

Use the Pythagorean theorem: \[a^2+b^2=c^2\]\[a=20,b=20\]\[20^2+20^2=c^2\]\[2*20^2 = c^2\]Take the square root of both sides:\[\sqrt{2*20^2}=\sqrt{c^2}\]We know \(c\) is positive, so we can simplify that to:\[20\sqrt{2} = c\]

OpenStudy (anonymous):

okay

OpenStudy (whpalmer4):

New square has the sides of length 16 instead of 20. What will \(c=\)

OpenStudy (whpalmer4):

Hint: in a 45/45/90 degree triangle such as we have here, the hypotenuse is always \(s\sqrt{2}\) where \(s\) is the side length

OpenStudy (anonymous):

16sqrt2

OpenStudy (whpalmer4):

Right. So how much did the diagonal decrease when the side length went from 20 to 16?

OpenStudy (anonymous):

4 sqrt 2

OpenStudy (whpalmer4):

There you go!

OpenStudy (anonymous):

THANK YOU! I have a few more.. Do you feel like helping? If not I understand

OpenStudy (whpalmer4):

if I didn't feel like helping, why would I hang out here? :-)

OpenStudy (anonymous):

Haha. true. THANK YOU! ~Simplify SQRT75x-SQRT3x+SQRT12x

OpenStudy (whpalmer4):

\[\sqrt{75x} - \sqrt{3x} + \sqrt{12x}\]Is that it?

OpenStudy (anonymous):

yes. I do not know how to do that, but yes

OpenStudy (whpalmer4):

okay, your job is to factor 75, 3, and 12 down to their prime factors. do you know how to do that?

OpenStudy (anonymous):

5 and the SQRT 3 SQRT 3 2 and the SQRt of 3

OpenStudy (whpalmer4):

Okay, you did more than I asked :-) \[\sqrt{75x} -\sqrt{3x} + \sqrt{12x} =\sqrt{3*5*5*x} - \sqrt{3*x} + \sqrt{2*2*3*x} \]\[= 5\sqrt{3x}-\sqrt{3x}+2\sqrt{3x}=\]

OpenStudy (anonymous):

7 and the SQRT of 3x?

OpenStudy (whpalmer4):

you fell into the trap :-) \[5a - a + 2a= \]

OpenStudy (anonymous):

ohhh o 6 and the SQRT of 3

OpenStudy (whpalmer4):

getting closer...but still not completely correct :-)

OpenStudy (whpalmer4):

a different way to look at it:\[5\sqrt{3x}-\sqrt{3x}+2\sqrt{3x} = \sqrt{3x}(5-1+2) =\]

OpenStudy (anonymous):

oh I left out the x in the SQRT of 3. I was like what am I doing wrong?1 Lol

OpenStudy (whpalmer4):

first rule of intelligent tinkering: save all the parts :-)

OpenStudy (anonymous):

THANK YOU! I have another one just like the last. ~ SQRT5x - SQRT20x = SQRT80x

OpenStudy (whpalmer4):

What's the ~ about?

OpenStudy (anonymous):

Oh it's just what I use to tell the problem

OpenStudy (whpalmer4):

\[\sqrt{5x} - \sqrt{20x} = \sqrt{80x}\]Are you supposed to solve for \(x\), or what?

OpenStudy (anonymous):

wait it should be minus SQRT 80 Sorry..

OpenStudy (whpalmer4):

so another simplify problem?

OpenStudy (whpalmer4):

\[\sqrt{5x} - \sqrt{20x} - \sqrt{80x}\] What are the factors of 5, 20, 80

OpenStudy (anonymous):

5 can go into all so SQRT 5 2 SQRT 5 4 SQRT 5

OpenStudy (whpalmer4):

you're up to your old tricks :-)

OpenStudy (anonymous):

Lol. sorry when you say that, that's what I think about.

OpenStudy (whpalmer4):

what happened to the \(x\)?

OpenStudy (anonymous):

x is in all of the SQRTs Sorry

OpenStudy (whpalmer4):

attention to detail...lack thereof will get you wrong answers very quickly!

OpenStudy (anonymous):

Okay. Sorry. So SQRT 5x 2 SQRT 5x 4 SQRT 5x

OpenStudy (whpalmer4):

So the final result is...

OpenStudy (anonymous):

Would the answer be -5 SQRT 5x

OpenStudy (whpalmer4):

You should use the equation editor button at the bottom left, it isn't hard...

OpenStudy (whpalmer4):

Yes, \[-5\sqrt{5x}\]

OpenStudy (anonymous):

\[-5\sqrt{5x}\]

OpenStudy (whpalmer4):

Or \[-5\sqrt{5}\sqrt{x}\]

OpenStudy (anonymous):

Thank you SOOOO much! You are amazing! That is all of my questions! THANKKK YOUU!!!

OpenStudy (whpalmer4):

You're welcome! I hope it sticks with you :-)

OpenStudy (whpalmer4):

Remember, don't lose the variables when simplifying :-) Might be best to factor the \(\sqrt{x}\) out up front: \[\sqrt{5x}-\sqrt{20x}-\sqrt{80x} = \sqrt{x}(\sqrt{5}-\sqrt{20} -\sqrt{80}) \]\[= \sqrt{x}(\sqrt{5}-2\sqrt{5}-4\sqrt{5}) = -5\sqrt{5}\sqrt{x}\]

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