T=2f(-2.5)=f(-0.5)=a-0.5f(4.5)=f(0.5)=|2/5-0.5|=0.1f(-2.5)=f(4.5)即a-0.5=0.1,a=0.6f(5a)=f(3)=f(-1)=-1+0.6=-0.4
