[tex]\it x^2-m^2x-5m^2-25=0 \Rightarrow (x^2-25)-m^2(x+5)=0 \Rightarrow \\ \\ \\ \Rightarrow (x-5)(x+5)-m^2(x+5)=0 \Rightarrow (x+5)(x-5-m^2)=0 \Rightarrow \\ \\ \\ \Rightarrow \begin{cases} \it x+5=0 \Rightarrow x_1=-5\\ \\ \it x-5-m^2=0 \Rightarrow x_2=m^2+5,\ \forall m\in \mathbb R\end{cases}[/tex]
