（1+1/x-2）÷(x²-1)/(2x-4)=(x-2+1)/(x-2)÷(x-1)(x+1)/2(x-2)=(x-1)/(x-2)×2(x-2)/(x-1)(x+1)=2/(x+1)=2/(√2-1+1)=2/(√2)=(√2)/2
