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问题: 数学问题

已知x+y分之x-y=2,求x+y分之3x-3y减x-y分之2×(x+y)

解答:

(3x-3y)/(x+y)-2(x+y)/(x-y)
=3*(x-y)/(x+y)-2/[(x-y)/(x+y)]
=3*2-2/2
=6-1=5.