解
xy=1/3
x-y=-1/6
(√x+√y)/(√x-√y)-(√x-√y)/(√x+√y)
=(√x+√y)²/(x-y)-(√x-√y)²/(x-y)
=[(x+2√xy+y)-(x-2√xy+y)]/(x-y)
=(4√xy)/(x-y)
=(4√1/3)×(-6)
=-8√3
a,b是方程两根
∴
a+b=6,
ab=4
a>b
∴a-b=√(a-b)²
=√(a+b)²-4ab
=√36-16
=2√5
(√a-√b)/(√a+√b)
=(√a-√b)²/(a-b)
=(a+b-2√ab)/(a-b)
=(6-4)/(2√5)
=√5/5