f(x)=x²-4x+5=(x-2)²+1当x=0或x=4时,f(x)=5x=2,f(x)取最小值=1所以,2<=m<=4
f(x)=（x-2）^2+1当x=0时f(x)为5，当0当24时f(x)>5综上所述：2<=m<=4
