Question

Acest exercițiu . Cu explicații .
Dau multe puncte !​

Answer 1

$\it A=\{\sqrt0,\ \sqrt1,\ \sqrt2,\ \sqrt3,\ ...\ \sqrt{20}\}\\ \\ B=\{x\in A;\ 1\leq x<3\}=\{\sqrt1,\ \sqrt2,\ \sqrt3,\ ...,\ \sqrt8\} \Rightarrow card(B)=8\\ \\ A\cap\mathbb{Q}=\{\sqrt0,\ \sqrt1,\ \sqrt4,\ \sqrt9,\ \sqrt{16}\}=\{0,\ 1,\ 2,\ 3,\ 4\}$