分式类题目:若1/x-1/y=3,求x-3xy-y/3x-2xy-3y=?

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分式类题目:若1/x-1/y=3,求x-3xy-y/3x-2xy-3y=?

若1/x-1/y=3,那么:
(y-x)/(xy)=3,即y-x=3xy
所以:x-y=-3xy
所以:(x-3xy-y)/(3x-2xy-3y)
=(x-y-3xy)/[3(x-y)-2xy]
=(-3xy-3xy)/(-9xy-2xy)
=(-9xy)/(-11xy)
=9/11