√(x²+1/x²+2）= √(x+1/x)²=|x+1/x|
x＞0时：= x+1/x
x＜0时：= -x-1/x看清题是减2√(x²+1/x²-2）= √(x-1/x)²=|x-1/x|x＜-1和0＜x＜1时：= 1/x - x-1≤x＜0或x≥1时：= x - 1/x