Question

1 si 2 va rooggg dau si coroanaaaa

Answer 1

1)

$(\frac{7}{12} - \frac{3}{10}) \cdot \frac{15}{34} = \frac{70 - 36}{120} \cdot \frac{15}{34} = \frac{34}{120} \cdot \frac{15}{34} = \frac{1}{8}$

2)

$Daca \ x \in \mathbb{N} \wedge x |5x + 7 => \exists k \in \mathbb{N}, astfel \ incat:\\\\5x + 7 = kx\\5x - kx + 7 = 0\\x(5-k) + 7 = 0\\x(5-k) = -7\\x = -\frac{7}{5-k} = \frac{7}{k-5} => \\k - 5 \in D_7, \ unde \ D_n \ multimea \ divizorilor \ lui \ n,\\\\D_7 = \{\pm 1, \pm 7\} => \\k - 5 = 1 \ sau \ k - 5 = 7, \ pentru \ ca \ x \in \mathbb{N}.\\k = 6 \lor k =12 => x \in \{1; 7\}$