f(x)=4x^2-mx+2
f(x)=(2x-1/4m)^2-1/16m^2+2
当x>=1/4m/2,即x>=m/8时,f(x)单调递增,
因此m/8>=1时满足条件,此时m>=8
答:实数m的取值范围是m>=8