原式={（x+1)/x}÷{x-(1+x²)/(2x)} = {（x+1)/x}÷{（2x²-1-x²)/2x} = {（x+1)/x}*{2x/(x²-1)}= {(x+1)/x}*{2x/(x+1)(x-1)} = {1/x}*{2x/(x-1)} = 2/(x-1)