若X是16的平方根,Y是（—3）平方的算术平方根
x=±4,y=3
代数式Y除以X+Y减去X除以x减去Y
y/(x+y)-x/(x-y)
x=-4
y/(x+y)-x/(x-y)=-25/7
x=4
y/(x+y)-x/(x-y)=-25/7