f(x)=log₁₀(ax²+ax+1)(1)定义域为R,则真数ax²+ax+1=a(x+½)²+1-a/4>0 恒成立∴0(2)若值域为R,则真数ax²+ax+1=a(x+½)²+1-a/4值域包含0和负值 且a>0(开口向上)∴a≥4
