V \( \mathbb{R} \) rieš rovnicu:
\( x^{2}-3 x=12 \)
\( K=\left\{\frac{3 \pm \sqrt{45}}{2}\right\} \)
\( K=\left\{\frac{5 \pm \sqrt{57}}{2}\right\} \)
\( K=\left\{\frac{3 \pm \sqrt{57}}{2}\right\} \)
\( K=\left\{\frac{3 \pm \sqrt{57}}{3}\right\} \)