求实数m的范围,使y=lg【mx²+2(m+1)x+9m+4】对任意x∈R恒有意义.
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![求实数m的范围,使y=lg【mx²+2(m+1)x+9m+4】对任意x∈R恒有意义.](/uploads/image/z/7134702-6-2.jpg?t=%E6%B1%82%E5%AE%9E%E6%95%B0m%E7%9A%84%E8%8C%83%E5%9B%B4%2C%E4%BD%BFy%3Dlg%E3%80%90mx%26%23178%3B%2B2%EF%BC%88m%2B1%EF%BC%89x%2B9m%2B4%E3%80%91%E5%AF%B9%E4%BB%BB%E6%84%8Fx%E2%88%88R%E6%81%92%E6%9C%89%E6%84%8F%E4%B9%89.)
求实数m的范围,使y=lg【mx²+2(m+1)x+9m+4】对任意x∈R恒有意义.
求实数m的范围,使y=lg【mx²+2(m+1)x+9m+4】对任意x∈R恒有意义.
求实数m的范围,使y=lg【mx²+2(m+1)x+9m+4】对任意x∈R恒有意义.
要求mx²+2(m+1)x+9m+4恒>0
当m=0时
2x+4>0对任意x∈R不恒成立
∴要求m>0
且Δ=4(m+1)^2-4m(9m+4)0
((4m-1)(2m+1)>0
m1/4
取交集
m>1/4
m的范围:m>1/4