[1]f(x1x2)=f(x1)+f(x2)
f(x*1)=f(1)+f(x),f(1)=0
f(x)=f(-x*-1)=f(-x)+f(-1)
f(1)=f(-1*-1)=2f(-1),f(-1)=0
f(x)=f(-x)
[2]x1>x2>0,x1=p*x2,p>1,f(p)>0
f(x1)-f(x2)=f(px2)-f(x2)
=f(p)+f(x2)-f(x2)=f(p)>0
[3]f(-0.4)=f(0.4)
f(7/4)=f(1.75)
f(1.75)>f(0.4)
f(7/4)>f(-0.4)