f(x)=log(1/2)x
[f(x)]^2>f(x^2)
[log(1/2)x]^2>log(1/2)x^2=2log(1/2)x
令log(1/2)x=a
a^2>2a
a^2-2a>0
a(a-2)>0
a2
log(1/2)x1
log(1/2)x>2=log(1/2)1/4
0