`25. a)`
`ĐK: m\ne 5`
`(m-5)x^2-4mx+m-2=0`
Pt có nghiệm
`⇔\Delta'=b'^2-ac\ge 0`
`⇔4m^2-(m-5)(m-2)\ge 0`
`⇔3m^2+7m-10\ge 0`
`⇔(3m+10)(m-1)\ge 0`
\(⇔\left[ \begin{array}{l}m\leq \dfrac{-10}{3}\\m\geq 1\end{array} \right.\)
`⇔m\in (-\infty; -10/3)∪[1; \infty)`