解析：已知x+y=3xy,那么：(2xy+y²)分之(x+y+3xy+3y²)=[y(x+x+y)]分之[(x+y)+3y(x+y)]=[y(x+3xy)]分之[(1+3y)(x+y)]=[xy(1+3y)]分之[(1+3y)(x+y)]=(xy)分之(x+y)=(xy)分之3xy=3