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liesnalibis
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Topic: Algebra Helpsolved. Thanks, Concrete_Rose! Posted: Dec 14 2013 at 1:59am 
I'm lost. Solve for s. I keep getting 7u4t but the answer's supposed to be 7u4t   2 8
Edited by liesnalibis  Dec 14 2013 at 2:55am


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liesnalibis
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Posted: Dec 14 2013 at 2:01am 
Concrete _Rose and others, I can show you how I did it if need be.


_ConcreteRose_
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Posted: Dec 14 2013 at 2:05am 
So I assume the question says to solve for S?
I would sart by multiplying each side by 4 That would give you 3s+4t= 5s+7u then add 5S to both sides: 3s(+5s) +4t = 5s(+5s) +7u 8s+4t=7u move the 4t to the other side of th equal sine 8s=7u4t then divide by 8 s=(7u4t)/8


liesnalibis
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Posted: Dec 14 2013 at 2:08am 
How do you know to multiply by 4? Is there a general rule?


liesnalibis
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Posted: Dec 14 2013 at 2:09am 
I feel so dumb right now. All this math is confusing me and making me forget stuff I thought I knew.


_ConcreteRose_
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Posted: Dec 14 2013 at 2:10am 
Well you know that multiplying by 4 get's rid of the denominator on BOTH sides. It's just easier to work with algebra when there are no fractions.
However, since the denominator is 4 just remember that multiplying by four on the left gives you negative 1. So when you divide by negative one, the signs change.
Edited by _ConcreteRose_  Dec 14 2013 at 2:10am


liesnalibis
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Posted: Dec 14 2013 at 2:13am 
_ConcreteRose_ wrote:
Well I know that multiplying by 4 get's rid of he denominator on BOTH sides. It's just easier to work with algebra when there are no fractions.
However, since the denominator is 4 just remember that multiplying by four on the left gives you negative 1. So when you divide by negative one, the signs change. 
You know what, I just figured that out when you were typing. I multiplied the whole left side by 1. I'll show you what I was doing then what I did if you can point out where I went wrong. I was looking at this problem for over an hour.


liesnalibis
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Posted: Dec 14 2013 at 2:33am 
Sorry for the wait...writing in Paint takes so long! But this is what I got when I did it like this. Can you tell me why this came out wrong?


liesnalibis
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Posted: Dec 14 2013 at 2:36am 
I figured since I multiplied both sides by the opposite denominator I could cross out the denominator and work with it that way. And the crazy thing is all the bait answers were similar (it is multiple choice) to my wrong answer, just with different signs.
Edited by liesnalibis  Dec 14 2013 at 2:38am


_ConcreteRose_
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Posted: Dec 14 2013 at 2:37am 
Okay, Well the first problem is this: what you do to one side you have to do to the other. If you multiply by positive 4 on one side, you have to multiply by positive 4 on the other. Or you could do negative 4 on both sides.
Secondly, you did the same thing you did on the other problem. What happened to the 4s in the denominators? If you cross out the 4s in the denominator you have to do the same in the numerator.
Edited by _ConcreteRose_  Dec 14 2013 at 2:39am

