x²+y²-8xy=0
所以
x²+y²=8xy
x²+2xy+y²=10xy
(x+y)²=10xy
x²+y²=8xy
x²-2xy+y²=6xy
(y-x)²=6xy
所以(x+y)²/(y-x)²=10xy/6xy=5/3
x>0,y>0
所以x+y>0
x>y,所以y-x
x²+y²-8xy=0
所以
x²+y²=8xy
x²+2xy+y²=10xy
(x+y)²=10xy
x²+y²=8xy
x²-2xy+y²=6xy
(y-x)²=6xy
所以(x+y)²/(y-x)²=10xy/6xy=5/3
x>0,y>0
所以x+y>0
x>y,所以y-x