Sea $A =\left\{a = q + \frac{1}{q }/ q \in Q^*,q > 0 \right\}$ , $A + A = \{a + b |a,b \in A\}$ , $A \cdot A =\{a \cdot b | a, b \in A\}$ . Demuestra que: i) $A + A \ne A \cdot A$ ii) $(A + A) \cap N = (A \cdot A) \cap N$ .