Question 68172
Problem 1:2s-2r/s^2-r^2
Factor where you can to get:
=[2(s-r)/(s-r)(s+r)]
Cancel the common factor of (s-r) to get:
=2/(s+r)
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Problem 2: a^2+1/a^4-1
Factor where you can to get:
(a^2+1)/[(a^2+1)(a^2-1)]
Cancel the common factor of (a^2+1)to get:
= 1/(a^2-1
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Problem 3:  6x^2y+9xy^2/12xy 
Factor where you can to get:
=[3xy(2x+3y)/12xy]
Cancel the common factor of 3, x, and y to get:
=(2x+3y)/4
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Cheers,
Stan H.