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#1 2013-07-16 08:41:52

bronxsystem
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combining algebra fractions

hey all i have very basic question but i dont understand why my answer is different



i get the answer



however the book says



why cant we remove the -d^2? is it because dividing both negative numbers makes a positive or something S:

Last edited by bronxsystem (2013-07-16 08:42:08)

#2 2013-07-16 10:08:24

bronxsystem
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Re: combining algebra fractions

i mean to reduce the fraction

eg 50/50 would just be 1/1 what rule am i missing with the -d^2

prob very silly question but cant get it out of my head


or

this is already reduced right? derp derp (:

Last edited by bronxsystem (2013-07-16 10:11:05)

#3 2013-07-16 12:36:41

bobbym
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Re: combining algebra fractions

Hi;

No, you can reduce that to 1 / 1 = 1


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

#4 2013-07-16 13:43:46

bronxsystem
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Re: combining algebra fractions

how would you write the final answer?



because if i just change the numbers its just 1/1 right S:

sorry i should stop posting after ive stayed up all night down

Last edited by bronxsystem (2013-07-16 14:47:58)

#5 2013-07-16 15:06:38

bobbym
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Re: combining algebra fractions

Hi;

I meant this one.


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

#6 2013-07-16 17:47:55

rete
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Re: combining algebra fractions

sorry to bug in, but here is were the logic you have fails, and the book is right
instead of having a-d and a+d, make the a-d=m and a+d=n
what you got:
d/m+a/n=(dn-am)/mn
ok, plug in the stuff
(d(a-d)-a(a+d))/((a+d)(a-d))
big excalmation point, sighn warnings
now if you split them the top part
da-dd-aa-ad=-dd-aa
bottom
(aa+ad-ad+dd)=aa-dd
simplification is only posible is some cases!!!
the a is a variable(wich i am assuming) so is b
if you go with a =7 and d = 1
thy them out
what do you have
7/(1+7)-1/(1-7)=7/8+1/6=25/24

to the formula you have got you get a minus(aa+dd) wich is allways negative or 0 and the solution is positive

#7 2013-07-17 01:33:34

bronxsystem
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Re: combining algebra fractions

hey rete thanks for reply

i followed what you wrote makes sense

big_smile

Last edited by bronxsystem (2013-07-17 01:42:58)

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