Question

Determinati elementele multimii:
A={ $\frac{}{xy}$ ∈N |$\frac{}{xy}=(x+y)^{2}-2$}

Answer 1

Cele doua cifre pot lua valorile:

$x\in \{1,2,3...,9\}\\ \\ y\in \{0,1,2,3,...,9\}$

Iei si verifici toate posibilitatile, de ex.:

$x=1\ \ y=0\ \ \ \Rightarrow \ \ \ 10=(1+0)^2-2\ \ \ \ (Fals)\\ \\ x=1\ \ y=1\ \ \ \Rightarrow \ \ \ 11=(1+1)^2-2\ \ \ \ (Fals)\\ \\ .........etc.........$

La final, bagi in multimea ceruta acele numere care au verificat relatia.