1<=x<=2
所以,0≤x-1≤1
0≤√(x-1)≤1
√(x+2√x-1) - √(x-2√x-1)
=√((x-1)+2√x-1 +1)- √((x-1)-2√x-1+1)
=√(√(x-1)+1)^2-√(√(x-1)-1)^2
=|√(x-1)+1|-|√(x-1)-1|
=(√(x-1)+1)-(1-√(x-1))
=2√(x-1)