- $ \\\left\\\{ {x \\\in \\\mathbb{R}|6{x^2}-7x + 1 = 0} \\\right\\\}$.
- $ \\\left\\\{ {x \\\in \\\mathbb{Q}|{x^2} - 4x + 2 = 0} \\\right\\\}$.
- $ \\\left\\\{ {x \\\in \\\mathbb{Z}|\\\left| x \\\right| < 1} \\\right\\\}$.
- $ \\\left\\\{ {x \\\in \\\mathbb{R}|{x^2} - 4x + 3 = 0} \\\right\\\}$.