- $ D = \\\left\\\{ {x \\\in R\\\left| {{x^2} - 2x + 1 = 0} \\\right.} \\\right\\\}.$
- $ C = \\\left\\\{ {x \\\in \\\mathbb{R}\\\left| {{x^2} - 5 = 0} \\\right.} \\\right\\\}$.
- $ A{\\\text{ }} = \\\left\\\{ {x \\\in \\\mathbb{N}\\\left| {{x^2} - 4 = 0} \\\right.} \\\right\\\}$.
- $ B = \\\left\\\{ {x \\\in \\\mathbb{R}\\\left| {{x^2} + 1 = 0} \\\right.} \\\right\\\}$.