已知X>Y,x2+Y2=4xy.求(X+Y)/(X-Y)=?
问题描述：
已知X>Y,x2+Y2=4xy.求(X+Y)/(X-Y)=?
答
x²+y²-2xy=2xy
(x-y)²=2xy
x²+y²+2xy=6xy
(x+y)²=6xy
(x+y)²/(x-y)²=3
又因为x＞y,x-y＞0
(x+y)/(x-y)=√3