∵x²-2xy-3y²=0∴*(x-3y)(x+y)=0∴x=3y 或x=-y（1）2x+y/x-2y 当x=3y时,原式=7y/y=7当x=-y时,原式=y/(-3y)=-1/3(2)2x2-3y2+5xy/x2+xy+y2=(2x+y)(x-3y)/(x²+xy+y²)当x=3y时,原式=0当x=-y时,原式=...