1
a=(根号2)-1 b=(2倍根号2)-根号6 c=(根号6)-2
a=√2-1 b=2√2-√6 c=√6-2
a=√2-1=√2(1-√2/2)
b=2√2-√6=√2(2-√3)
c=√6-2=√2(√3-√2)
b-a=√2[2-√3-(1-√2/2)]=√2(3-√3+√2/2)
√2>1,3-√3>1
b-a>1
a-c=√2(1-√2/2-√3+√2)=√2(1+√2/2-√3)
=√2(2+√2-2√3)/2>0
a-c>0
b>a>c
2
xy=1,x=2+根号3
y=1/(2+√3)=2-√3
(1/x+1)+(1/y-1)
=y-1+x+1/(x+1)(y-1)
=x+y/(xy-x+y-1)
=1/(1-2-√3+2-√3-1)
=1/-2√3
=-√3/6
3
化简√5+2√6-√5-2√6
=√((√3)^2+2√6+(√2)^2)-√((√3)^2-2√6+(√2)^2)
=√(√3+√2)^2-√(√3-√2)^2
=√3+√2-(√3-√2)
=2√2
2