已知x-y=2xy,求代数式3x-5xy-3y/x+xy-y的值

x-y=2xy
3x-5xy-3y/x+xy-y
=[3(x-y)-5xy]/[(x-y)+xy]
=(6xy-5xy)/(2xy+xy)
=1/3
1/x+1/y=4
y+x=4xy
x-5xy+y/2x+xy+2y
=[(x+y)-5xy]/[2(x+y)+xy]
=(4xy-5xy)/(8xy+xy)
=-1/9