f(x)=1/[2^x+2^(1/2)]
f(x+1)=1/[2^(x+1)+2^(1/2)]
f(-x)=1/[2^(-x)+2^(1/2)]=2^x/[1+2^(x+1/2)]
f(x+1)+f(-x)=√2/2
所以f（-5）+f(-4)+...+f(0)+...+f(5)+f(6)= =3√2