F(x)为偶函数,则x>0时,f'(x)>x,记g(x)=f(x)+1/2-f(1-x)-x,则f(1/2)=0,对g(x)求导再讨论0=1时情况,当x>1时,用f'(x-1)+2(1-x)替代f'(1-x)即可