x+4√y=2√(x-y)
x²+8√y*x+16y=4(x-y)
即x²+(8√y-4)x+20y=0
{Δ=(8√y-4)²-80y≥0
{y≥0
==>
64y-64√y+16-80y≥0
y+4√y-1≤0
==>
0≤√y≤√5-2
==>
0≤y≤9-4√5
x+4√y=2√(x-y)
x²+8√y*x+16y=4(x-y)
即x²+(8√y-4)x+20y=0
{Δ=(8√y-4)²-80y≥0
{y≥0
==>
64y-64√y+16-80y≥0
y+4√y-1≤0
==>
0≤√y≤√5-2
==>
0≤y≤9-4√5