Question

If $A=\{1,2,3\},B=\{3,4\}$
find (A $\times$ B) $\cup$ (B $\times$ A)

• A. $\left\{\right(1,3),(2,3),(3,3),(1,4),(2,4),(3,4),(3,1),(4,1),(3,2),(4,2),(4,3\left)\right\}$
• B. $\left\{\right(2,3),(3,3),(1,4),(2,4),(3,4),(3,1),(4,1),(3,2),(4,2),(4,3\left)\right\}$
  
• C. $\left\{\right(1,3),(2,3),(3,3),(1,4),(2,4),(3,4),(3,1),(4,1),(4,2),(4,3\left)\right\}$
• D. None of these

Answer 1

The correct option is A $\left\{\right(1,3),(2,3),(3,3),(1,4),(2,4),(3,4),(3,1),(4,1),(3,2),(4,2),(4,3\left)\right\}$

$(A\times B)=\left\{\right(1,3),(1,4),(2,3),(2,4),(3,3),(3,4\left)\right\}$

$(B\times A)=\left\{\right(3,1),(3,2),(3,3),(4,1),(4,2),(4,3\left)\right\}$

$\Rightarrow (A\times B)\cup (B\times A)=\left\{\right(1,3),(1,4),(2,3),(2,4),(3,3),(3,4),(3,1),(3,2),(4,1),(4,2),(4,3\left)\right\}$