Question

Vă rog ajutor! Dau coroană! Ex 6 vă rog! ​

Answer 1

5.

$\it a,\ b\ -\ numere\ \ prime.\\ \\ 3a+12b=66\bigg|_{:3} \Rightarrow a+4b=11 \Rightarrow a=3,\ \ b=2.$

6.

$\it n\in \mathbb{N}^*,\ \ n\ \vdots\ 3 \Rightarrow n\in\{3,\ 6,\ 9,\ 12,\ 15,\ 18,\ 21,\ ...\}\ \ \ \ (*) \\ \\ x < 19\ \stackrel{(*)}{\Longrightarrow} A=\{3,\ 6,\ 9,\ 12,\ 15,\ 18\}\\ \\ \\ 18\ \vdots\ y \Rightarrow B=\{1,\ 2,\ 3,\ 6,\ 9,\ 18\}\\ \\ A\cup B=\{1,\ 2,\ 3,\ 6,\ 9,\ 12,\ 15,\ 18\}\\ \\ A\cap B=\{3,\ 6,\ 9,\ 18\}\\ \\ A\setminus B=\{12,\ 15\}$