已知x的-1次方-y的-1次方=?
--------------------------题目不全
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x的-1次方-y的-1次方=-3
1/x-1/y=-3
y-x=-3xy
x-y=3xy
(2x+3xy-2y)/(x-2xy-y)
=(6xy+3xy)/(3xy-2xy)
=9xy/xy
=9