f(-5)=-f(5)=-f(1*2-5)=-f(-3)=f(3)=f(-1)=-f(1)=-1f(6)=f(-4)=-f(4)=-f(-2)=f(2)=f(0)=0f(log(2)7)=f(2-log(2)7)=f(log(2)(4/7))=-f(log(2)(7/4))=-log(2)(1+log(2)(7/4))>-1所以f(-5)最小，f(6)最大
