Question

Fie A si B doua multimi . Daca card A ori card (A/B)=14 . Determinati card ( A intersectat cu B )

Answer 1

card A= card A\B + card (A∩B)
deci

cardA≥card A\B
cardA*card A\B=14 =14*1=7*2

  14= 14*1

caz I
card A=14, card A\B=1
card A= card A\B + card (A∩B)
14=1+card (A∩B)
card A∩B=13

caz II
card A=7 , card (A\B)=2

cardA= card (A\B) +card (A∩B)
7=2+card (A∩B)
card (A∩B)=5