f(x)=lg[(m^2-3m+2)x^2+2(m-1)x+5],若f(x)的值域为R,则实数x的取值范围是?

(m^2-3m+2)x^2+2(m-1)x+5>0
令g(x)=(m^2-3m+2)x^2+2(m-1)x+5
f(x)的值域为R
g(x)要取得大于0的所有值
b^2-4ac=4(m-1)^2-20(m^2-3m+2)
=4(m-1)(9-4m)>=0
m=1时f(x)=lg5(舍)
(1,9/4]