若函数y=log2[ax2+(a-1)x+1/4]的值域为R,求实数a的取值范围

问题描述:

若函数y=log2[ax2+(a-1)x+1/4]的值域为R,求实数a的取值范围

要使原函数值域为R,则[ax2+(a-1)x+1/4]能取到(0,+无穷)一切值
显然a=0满足上述条件,a0时,
若a>=1,可知[ax2+(a-1)x+1/4]不能取到(0,+无穷)一切值
若0