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