[tex]x^2-4mx+1=0\\
\text{O ecuatie de gradul 2 are solutii reale atunci cand delta e mai mare }\\
\text{ sau egal cu 0.}\\
\Delta=16m^2-4\\
\Delta\geq 0\\
16m^2-4\geq 0\\
16m^2\geq 4\\
m^2\geq \dfrac{1}{4}\\
|m|\geq \dfrac{1}{2}\\
S:m\in \left(-\inf; -\dfrac{1}{2}\right]\cup \left[\dfrac{1}{2}; \inf\right)[/tex]