√[a+2√(a-1)]+√[a-2√(a-1)]=√[a-1+2√(a-1)+1]+√[a-1-2√(a-1)+1]=√[√(a-1)+1]^2+√[√(a-1)-1]^2=|√(a-1)+1|+|√(a-1)-1|若1<=a<=2则原式=2若a>2则原式=2√(a-1)
