已知x的平方加3xy减4y的平方等于0,(y不等于0),试求x-y/x+y即：X^2+3xy-4y^2=(x+4y)(x-y)=0x+4y=0或x-y=0；x=-4y或x=y将x值代入算式x-y/x+y ：1、(-4y-y)/(-4y+y)=5/32、(y-y)/(y+y)=0.(y不等于0)答案为5/3或0....