f(x)=a^x(a^x-3a^2-1) 设t=a^x f(t)=t(t-3a^2-1)=[t-(3a^2+1)/2]^2-(3a^2+1)^2/4 当a>1时,x∈[0,+∞),t∈[1,+∞),单调增.要使得f(x)单调增,只要f(t)在[1,+∞)单调增,则 (3a^2+1)/2≤1,得-√3/3≤a≤√3/3,矛盾 当0...