Question

If $A=\{1,3,4,6,7\},B=\{2,5,6,8\}$ and a relation $R=\left\{\right(x,y);(x,y)$$ϵA\times B,y=2x\}$ then write $R$ in roster form

Answer 1

$A=\{1,3,4,6,7\}$

$B=\{2,5,6,8\}$

$R=\left\{\right(x,y);(x,y)ϵA\times B,(y=2x\left)\right\}$

when $x=1$

$y=2\times 1$

$=2$

$(1,2)$

when $x=3$

$y=2\times 3$

$=6$

$(3,6)$

when $x=4$

$y=2\times 4$

$=8$

$(4,8)$

when $x=6$

$y=2\times 6$

$=12$( 12 is not an element of set B)

So, $R=(1,2),(3,6),(4,8)$