f（-x）=1/（2^-x+√2)=2^x/1+2^(x+ 1/2)
f(1+x)=1/[2^ (1+x ) +√2]=1/√2[1+2^(x+ 1/2)]
两式相加为（2^x *√2+1）/√2[1+2^(x+ 1/2)]
=1/根号2