(a+b)/(a-b) - (a-b)/(a+b) = ...
the common denominator for both fractions is (a-b)(a+b)
=> multiply the first fraction (top and bottom) by (a+b) and the second one by (a-b)
= (a+b)·(a+b)/(a-b)·(a+b) - (a-b)·(a-b)/(a+b)·(a-b) =
= (a+b)² /(a-b)·(a+b) - (a-b)² /(a+b)·(a-b) =
= [ (a+b)² - (a-b)² ] /(a-b)·(a+b) =
= [ a² + 2ab + b² - (a² - 2ab + b²) ] /(a-b)·(a+b) =
4ab /(a-b)·(a+b)
(or 4ab /(a²-b²) )
Hope this helps.
2007-05-02 07:11:47
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answer #1
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answered by M 6
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I think you are not distributing correctly somewhere in your 7 pages.
You need to get the common denominator, which will be (a+b)(a-b) and that equals a^2-b^2.
Your first fraction is then (a+b)(a+b) / (a-b)(a+b) which equals (a^2+2ab+b^2) / (a^2-b^2).
Your second fraction is (a-b)(a-b) / (a-b)(a+b) which equals
(a^2-2ab+b^2)/(a^2-b^2).
Subtract them, and the numerators give
(a^2+2ab+b^2) - (a^2-2ab+b^2) = a^2 + 2ab + b^2 - a^2 + 2ab - b^2 = 4ab.
Therefore your answer will be 4ab / (a^2-b^2)
2007-05-02 07:18:45
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answer #2
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answered by Anonymous
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You are required to subtract two fractions
You need a common denominator (a+b)(a-b)
Multiply top and bottom of first fraction by a + b
Multiply top and bottom of second fraction by a - b
You will then have
(a+b)(a+b)/ (a+b)(a-b) minus (a-b)(a-b)/(a+b)(a-b)
numerator is (a^2 + 2ab + b^2) minus (a^2 - 2ab + b^2)
denominator is (a + b)(a - b)
numerator simplifies to 4ab so your answer is
4ab/[(a+b)(a-b)]
2007-05-02 07:22:44
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answer #3
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answered by fred 5
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(a + b) / (a - b) - (a - b)/(a + b)
You need a common denominator of (a - b)(a + b)
So...
The first fraction becomes:
(a + b)(a + b) / (a - b)(a + b)
= (a^2 + 2ab + b^2) / (a - b)(a + b)
And the second one:
(a - b)(a - b) / (a - b)(a + b)
= (a^2 - 2ab + b^2) / (a - b)(a + b)
Now, you're subtracting those.... I'm just going to work on the numerators for a minute...
(a^2 + 2ab + b^2) - (a^2 - 2ab + b^2)
= a^2 + 2ab + b^2 - a^2 + 2ab - b^2
(Make sure you distribute that minus sign correctly!!!)
= 4ab
So, the final answer is
4ab / (a - b)(a + b)
2007-05-02 07:14:56
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answer #4
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answered by Mathematica 7
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First, please verify that the parentheses that I have inserted correctly describe the expression:
f = (a+b)/(a-b) - (a-b)/(a+b).
Multiply and divide through by (a+b)(a-b) to get:
((a+b)^2 - (a-b)*2)/((a+b)(a-b))
Expand the numerator and denominator:
(a*2 + 2ab + b*2 - a*2 + 2ab - b*2)/(a^2 - b^2)
Collect terms:
4ab/(a^2 - b*2). Done.
2007-05-02 07:20:14
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answer #5
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answered by Anonymous
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2016-12-05 05:48:47
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answer #6
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answered by headlee 4
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I think you mean (a+b)/(a-b) - (a-b)/(a+b), in which case
[(a+b)(a+b)] / [(a-b)(a+b)] - [(a-b)(a-b)] / [(a+b)(a-b)] =
= [(a+b)^2 - (a-b)^2] / [(a-b)(a+b)]
= [a^2 + 2ab + b^2 - (a^2 - 2ab + b^2)] / [a^2 - ba + ab - b^2]
= (4ab) / (a^2 - b^2).
2007-05-02 07:17:26
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answer #7
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answered by victeric 3
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Call Me Pete is correct (dang, not fast enough!)
You could FOIL the bottom into what John, M, and Adam have, though. I think some of these people are changing their answers to be correct lol
2007-05-02 07:17:14
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answer #8
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answered by Randy 4
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(a+b/a-b) - (a-b/a+b) =
= (a+b)*2 - (a-b)*2 /(a-b)(a+b) =
= a*2+2ab+b*2-a*2+2ab-b*2/(a-b)(a+b)
= 4ab/(a-b)(a+b)
*2 means exponent
2007-05-02 07:33:15
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answer #9
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answered by jasmina z 1
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(a+b/a-b) - (a-b/a+b)
= [(a+b)^2/(a-b)(a+b)] - [(a-b)^2/(a+b)(a-b)]
= [(a+b)^2 - (a-b)^2] / (a+b)(a-b)
= [a^2 + 2ab + b^2 - a^2 + 2ab - b^2] / (a+b)(a-b)
= 4ab / (a^2 - b^2)
2007-05-02 14:09:06
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answer #10
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answered by Kemmy 6
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