m为实数,试比较代数式3/2m+1和1/m^2-m+2的大小
(3/2m+1)-(1/m^2-m+2)
=[3(m^2-m+2)-(2m+1)]/(2m+1)(m^2-m+2)
=[3m^2-3m+6-2m-1]/(2m+1)(m^2-m+2)
=[3m^2-5m+5]/(2m+1)(m^2-m+2)
=3[m^2-5/3m+(5/6)^2-(5/6)^2+5/3]/(2m+1)(m^2-m+1/4-1/4+2)
=3[(m-5/6)^2+35/36]/(2m+1)((m-1/2)^2+7/4)
(m-5/6)^2+35/36>0
(m-1/2)^2+7/4>0
(1)当2m+1>0即m>-1/2时
上式>0
(3/2m+1)>1/(m^2-m+2)
(2)当2m+1-1/2时
上式